DECEMBER 1955

A COMPARISON BETWEEN REPRODUCED AND "LIVE" MUSIC

by R~ VERMEULEN. 534.76: 534.86: 681.84.087.7

Endeavours to realizefidelity in ihe transmission of music are of long standing. 'rhe subjectaroused interest as long ago !ls 1881, when Parisians were giv~n the opportunity of listeningto telephone transmissionsfrom the Grand Opera via an installation designed by Ader. Althoughstill very imperfect, the installation had already one modern refinement: it was equipped for"binaural" hearing. From these beginnings stereophonic reproduetion. has been developed,nowadays generally recognized as essensial to the natural reproduction of music .. The prerequisites for the natural reproduction of music have recently been re-examined in

. this labortuory . From alternate performances of "live" music and music reproduced with the_ most modem equipment in the same hall, it was found that in many cases the listeners could hear

no difference between them and sometimes systematically confused the two.

Why is it that in spite of all technical progress inelectro-acoustics, it is still possible to distinguishbetween the music heard from a loudspeaker andthat heard in the concert hall? Many will havetheir answer ready to this question. They willpoint out that die music is distorted in the variouslinks of the reproduction ' channel: microphones,amplifiers, tape recorder or gramophone, and aboveall by the loudspeakers. These devices fall short inthe reproduetion of very low and very high notes,'and, moreover, they introduce alien sounds. Thedynamic range is restricted on the one .hand, byhum and noise, and, on the other, by combinationtones, which arise from overloading.

It cannot be denied that even in the best repro-ductions of to-day these distortions are still present.Nevertheless we doubt whether our question can beanswered by simply laying the blame upon theshortcomings of electro-acoustical apparatus. Thepossibility of measuring certain shortcomings ob-jectively. and quantitatively (such as the lack ofhigh overtones) has been a great stimulus forimprovement. But the uncertainty regarding thepermissible magnitude of these imperfections makesit very tempting to regard them as the only causeof the musically not entirely satisfactory result.The danger then is that the electrical engineer willtreat the electro-aco~stical instrument as a linkbetween a signal generator and a voltmeter, andimpose requirements upon it which, from a musicalpoint of view, are meaningless, or even erroneous.A typical example of such a misconception was thetendency, very prevalent among technicians at thetime but now discarded, to regard hiss as a criterionfor a good reproduetion of high tones, and thus toconsider a high noise level as a favourable ratherthan as an adverse characteristic.

The "hole in the wall"It may therefore be wise to look for other answers

to the above question. Are we sure, for example,that a reproduetion channel with no measurabletechnical defects will he able to ·create the illusionthat an orchestra is playing actually in the room?Might there not be other aspects, so far neglected,which impair musical appreciation more than minortechnical imperfections?

Some investigation into the problem shows thatit is possible to give a satisfactory reproduetion of asingle, small, spatially concentrated sound source,such' as a human voice or one small instrument,such as a clarinet, on condition that it is reproducedat the original volume. With a small ensemble andespecially with a large orchestra, however, some-thing is lacking in the reproduetion as heard fromthe loudspeaker. The reason is that even a perfectloudspeaker can do 11;0 more than imitate the vibra-tions picked up by the microphone, and thus thebest result will only be equivalent to a hole in. thewall of the concert hall. The sound that such anopening transmits is absolutely free from allelectrical and mechanical distortion, and shouldtherefore certainly'be designated as "super-highestfidelity". Nevertheless, the concert-goer who hasarrived too late and who has had to listen to thebeginning of the concert through a chink in the door,is relieved when he can enter the concert hall. Thus,irrespective of technical imperfections, there isevidently something missing with music, originatingfrom an' extensive sound-source, that reaches ourears via a small opening.

It is now generally known that this lack ofauditory perspective can be rectified by means ofstereophonic reproduction. A number. of articles onthis subject have appeared in this Review, in 1939

171

172 PHILlPS TECHNICAL REVIEW

and in later years. Before describing some compara-tive tests made with stereophonically reproducedmusic and "live" music, we may usefully recapitu-late the principles of stereophonic reproduction. Weshall start with its predecessor: binaural reprodur-tion.

Binaural hearing

To improve loudspeaker reproduetion it is firstlynecessary to overcome the "hole-in-the-wall" effect.This can be done by using two microphones insteadof one. The microphones may be placed as ears onan "artificial head" (jig. 1) and connected to a pairof headphones in such a way that the left ear hearsthe sounds picked up by the left-hand microphoneand the right ear the sounds picked up by the right-hand microphone. In this way "binaural" hearing,i.e. with two ears (fig. 2), is restored. True, there areonly slight differences between the sound heard inthe left earpiece and that in the right, but they arequite sufficient to give the listener the impressionthat he is seated at the place where the artificialhead is set up. He may, for instance, easily be giventhe sensation that he hears persons moving andtalking behind him, although there is no one there.The impression may be so realistic that the listenerhas to turn round to convince himself that there isreally no one there. But as soon as he does so, theshortcomings of this system become evident, viz:the whole acoustical world rotates with his head.

VOL. 17, No. 6

To avoid this, one might arrange for the artificialhead to turn with the listener's head, and tests haveconfirmed that this does in fact overcome thedeficiency 1); moreover, the listener can then distin-

I? ~.@)=w

I 1I

HL) ,,=IU~ f,=

~ ,

84698

Fig. 2. Binaural hearing. The music played in room I is heardby the listener in 11 via headphones, each ear-piece of whichis connected to a microphone. He thus receives an impressionof auditory perspective, The microphones should preferablybe fitted on an artificial head (IJ).

guish between sound-sources III front of him andbehind him, which he cannot do if he keeps hishead still. The disadvantages of this otherwise idealsolution are, however, obvious: headphones are Inthemselves a nuisance - and the coupling of the

1) K. de Boer and A. Th. v. Urk, Philips tech. Rev. 6, 359-364, 1911, in particular, pp. 360, 361.

Fig.1.Plaster heads, dating from the early days of stereophony and intended asexperimental artificial heads. (They represent two workers who have contributed tothe development of stereophony: on the left, K. de Boer; on the right, A. T. van Drk.)It was soon found that a sphere constitutes an adequate approximation to the human head.The photograph in the middle shows a modern artificial head.

DECEMBER 1955 REPRODUCED AND "LIVE" MUSIC

artificial head with the listener's head would bequite impracticable. Nevertheless, these experi-ments were very instructive, showing as they didhow essential is our binaural hearing to the soundimpression received. .

On the manner in which binaural hearing enablesus to determine the direction of the sound-source,there have long been differences of opinion. It hasbeen demonstrated by experiments that a timedifference between the signals reaching the left andthose reaching the right ear produces a sensation of .direction, but others have shown that this is like-wise the case with a difference in intensity. K. deBoer 2), who has made a thorough study of thesubject in this laboratory, was able to confirm thatboth parties were right, that is to say that differencesboth in time and intensity contribute to directionalhearing, The remarkable thing is that these contri-butions are additive: the angle from which a sound.seems to come, owing to a time difference, becomesgreater or smaller as the effect of a superimposedintensity difference works in the same or in theopposite direction. It is even possible to let the twoeffects compensate each other; thus, a sound-source apparently heard from a certain angle as aresult of a time difference, can he made to "return"to the centre by means of an opposing intensitydifference.

StereophonyI

A second remarkable effect noted by K. de Boeris that the sound stimuli which the ears receive fromtwo loudspeakers, placed some yards apart and eachconnected to a microphone on an artificial head, arementally interpreted as a single apparent sound-source, which appears to lie in between the two realones. This helped to clarify the mechanism involvedin obtaining three-dimensional acoustic effects usingtwo loudspeakers instead of headphones (fig. 3).Stereophonic reproduetion giving the impressionthat the sounds come from various directions was. achieved by Fletcher and Sto'kowski as long ago as19333).

The explanation of the effect given at the rime, however, isnot entirely convincing. It may be briefly restated as follows.Suppose that in a concert hall a curtain is hung which isimpervious to sound and which is provided, at the side facingthe orehestra, with a large number of mierophones. Eachmicrophone is connected to a loudspeaker at the other side of

2) K. de Boer, Stereophonie sound reproduction, Dissertation,Delft, 1940.

3) Symposium on wire transmission of symphonic music andits reproduetion in anditory perspective: H. Fletcher,Basic requirements, Bell Syst. tech. J. 13, 239-244, 1934.

I

H

173

JI

@l~.~.~.

~c@J ••

84699

Fig. 3. Stereophony. Each mierophone on the artificial head(H) in hall I is connected to its own loudspeaker (L1, L2) inhall 11.Here too, the audience in 11receives a spatial impressi-on of the sound.

the curtain (fig. 4). Sound waves picked up by the microphonesare then radiated at the other side by. the loudspeakers, andthus proceed as ~f the curtain were not present. If such acurtain with loudspeakers is set up in another hall, the samesound fieldwiIIbe set up as behind the curtain in the first hall.As there is a limit to the number of microphones, transmissionchannels and loudspeakers whieh can be installed, one has tomake do with a rough approximation, for which three micro-phones and three loudspeakers were found to be sufficient.

Listening to the result of such an arrangement, and moreoveron learning that the result is particularly good when using only-two channels (two microphones and two loudspeakers), it isdifficult to understand, if the above explanation were complete,how such a goodapproximation is obtained with sofewchannels.In our opinion we cannot leave out of consideration the psy-chologicalphenomenon that the four sound-stinmli received-byboth ears from the two loudspeakers are interpreted as comingfrom one single source 4). It is thus not necessary to produce a

p ~£Jf> TT~a.

I ][

.4737

Fig. 4. Explanation ,of stereophony according to an Americanview. A is an imaginary "curtain", one side being fully taken.uP by microphones, the other by loudspeakers. Each micro-phone is linked via its own channel to the corresponding loud-speaker at the other side of the curtain, and also to a similarloudspeaker on "curtain" B in hall 11. Thus, the same soundfield is produced in hall 11 as in hall 1. Practical stereophony,necessarily using only a small number of channels, would onlybe a rough approximation to the ideal case outlined.

4) K. de Boer, Stereophonic sound reproduction, Philipstech. Rev. 5, 107-114" 1940.

174

,," r ,

PHILIPS TECHNICALREVIEW ~ VOL. 17, No. 6

replica of the sound in the room; it is enough if we aim atsupplying the two ears with a set of signals that are perhapsdifferent from the original ones but still create the same im-pression, According to the earlier explanation, three channels, would give a better approximation than two, four. a betterapproximation than three, and so on, whereas out experienceis that two channels give a clearer and, above all, a "sharper"sound image than three. To avoid misunderstanding weshould add that the use of more than two loudspeakers canstill be advantageous, e.g. in order to produce a stereophoniceffect for a large audience. ./'

If the two microphones are mounted without theartificial head between them, the differences of inten-sity _between the signals which they pick up becomemuch smaller, these differences having been mainlythe consequence of the shielding effect of the artificialhead. The stereophonic effect must now rely primarilyon the time differences. To suggest the same directionthese must be strongly exaggerated, which can he.done by making the distance between the. micro-phones about three times as large as in the artificialhead. It is surprising that. the ear is able to interpret. as directions such large time differences, although itcan never have had the opportunity to acquire thefaculty. In natural directional hearing the timedifference is always less than 0.6 milliseconds andcontributes only about 10% to the perception ofdirectio:O:. An artificial head thus supplies lessabnormal signals than two separate microphones,and moreover, as a compact unit, it is easier tohandle. The size of the artificial head is only inspecial cases the same as that of the human head.It can best be chosen in accordance with theset up and the size of the orchestra, following thisempirical rule: if cpis the angle, (in degrees) subtendedat the head by the orchestra (fig. 5), then thehorizontal diameter of the artificial head must be(2000jcp) cm, and the distance between two freely-mounted microphones must be (6000jcp) cm 5).

In the reproduetion of music the conscious per-ception of direction, as made possible by stereo-phony, does not play a very significant role: after all,for the audience in a concert hall, appreciation ofthe. performance is not critically dependent on theprecise positioning of all the instruments. It is there-fore 'not so very important that the directions are .reproduced accurately. The reason' why stereo-phonic reproduetion gives. a significant improvementis that the instrumènts are heard distinct from eachother in space instead of as a muddle of sounds."Our "hole in the wall" has now become as it were alarge window that enables the listener to surveyaurally the whole or' the orchestra.

S) K. de Boe~, The formation of stereophonic images, Philipstechno Rev. 8, 51-56, 1946.

Another remarkable fact is that with stereo-phonic reproduetion one can concentrate effortlesslyon sound from a certain direction and detach one'sattention from unwanted sounds (noise, hiss,reverberation, etc.) from other 'directions. It isstriking how loud the noise in the studio seems whenheard from one loudspeaker, how much more awareone becomes of reverberation, and how soon soundsbecome unintelligible when two or more persons aretalking at the same time, whereas these phenomena

. are hardly noticed if one is in the studio oneself orif one listens to a stereophonic transmission.

84525bFig. 5. a) The artificial head If "sees" an ensemble of musiciansat a subtended angle tp, The most favourable horizontal dia-meter of the artificial head is 2000jt:p cm (t:p in degrees); theacoustic representation of the five musical instruments MI ...Ms is thcn as shown in (b), between the loudspeakers' L1 andL2•

Room acoustics

May we now expect that the stereophonic repro-duetion of orchestral music will be indistinguishablefrom the original - assuming, of course, that everyattention has been paid to all details of the electro-acoustical installation '?This will 'certainly not he the case if the repro-

duetion takes place in a hall or room whose acousticproperties are inadequate. It is generally recognizedthat the acoustics of a concert hall constitute animportant element in the appreciation of music; wecannot therefore expect the imitation of an orchestrato do without this support.

It might he presumed that certain shortcomings inthe acoustics of the room where the music is to hereproduced could be rectified by resorting toelectro-acoustical aids. We shall Ieave this subjectto a subsequent paper and proceed now to describetests.' in which "live", and reproduced music werecompared together. As both were played in thesame hall, the influence of room acoustics wasexcluded.

Comparative tests

In order to ascertain objectively to what extent astereophonic installation is capable of imitatingactual musical instruments, we invited 300 personsto the Philips Laboratory to make a comparison

, I

DECEMBER 1955 REPRODUCED AND "LIVE" MUSIC 175

between the reproduetion of stereophonically re-corded pieces of music and the same pieces playedby a small ensemble, seated behind a thin butopaque curtain. The greatest care was spent on therecording' of the music, so that it would really hethe best possible replica of the ensemble, particularattention being paid to the setting up of the artificialhead. Naturally, the reproduetion had to be just asloud as the actual music. The entire reproduetionapparatus remained in operation all the time inorder to prevent switching clicks and perhaps achange, however small, in the level or the characterof the room-noise, from giving some listeners a clue.The recordings (on tape) were therefore made withlong periods distributed arbitrarily between them;during these blank periods, the tape still running,the live music was played by the musicians.

The procedure was a follows. The same, shortpiece of music (15 to 30 seconds) was renderedtwice, both stereophonically and by the musicians,but in arbitrary order, each piece of music beingindicated in chronological order as "reproductionA" and "reproduction B" ("reproduction" thusincludes the live performance. The listeners werenot aware that "live" music would he played).Immediately afterwards, there followed, as "repro-duetion X", a repetition of either A or B. The liste-ners then had to answer; within about one minute,the following questions presented to them on aquestionnaire:I) Was X the same as A or the same as B?II) Which of the two reproductions, A or B, was

the more natural?The first question merely requires the listener to

hear a difference between the actual and the repro-duced music, whereas the second question requiresthat he should moreover have an idea of how "live"music sounds. At each session, ten pieces of.musicof different kinds (chamber music, dance music)were played, the number of musicians varyingslightly.After the experiments were concluded, the right

answers returned were marked with the number 1and the wrong ones with 0 and the means taken ofthe totals. -The result was 0.75 for the first questionand 0.71 for the second question. If it is borne inmind that an average of 1 for the first questionwould mean that every participant in the experimentalways heard a' difference between "live" and repro-duced music, and that a result of 0.5 means that noparticipant heard any difference whatsoever andeverybody was therefore guessing, it appears thatthe result obtained (0.75) lies midway between thesetwo extremes. Thus, the average of 75 correct ans-

wers out of a hundred cases can he comprised of 50correct "decisions" and 25 lucky guesses. Relatively. few persons (16%) were able to hear the differenceinfallibly, and even they found it rather difficult.To recognize the "live" music as the more "natural"appeared to be even more difficult, as was shown bythe average of 0.71 for the second question.

40

/'\

1 \\

1 /N1

/J ~

AI \\

/j v-\

If \\/v

V 1/..... .,..

80Y

Î60

2 4 6 8 TO-xFig. 6. Full curve: number of persons y, on an average perseries of ten tests, that gave x correct answers to question I,plotted as a function of x. Dashed curve: probability distribu-tion (binomial curve) taking 0.75 as an average of all answersto question I. Total number of participants in the tests: 310.

The results of a statistical treatment of theanswers are represented graphically by the fulllinesin fig. 6 (question I) and fig. 7_ (question II). Thenumber of listeners, y, who gave x correct answersto the ten questions is plotted as a function of x; atotal of more than 300 persons participated in theexperiments. If there had been no mutual differencesbetween the participants, and no differences in

y

I/ "/

I \I ,

I \~ r-,I V,I 10-

V 1\// \ ',

/ l""- t \I

V '"- j,'" .

80

60

40

20

2

....'"~

8 la_X

4 6

Fig. 7. As fig. 6, but applicable to question 11, and with 0.71as average. Total number of participants: 308.

176 PHILlPS TECHNICAL REVIEW VOL. 17, No. 6

difficulty between the successive tests, we shouldhave had a curve determined exclusively by chance,that is to say a binomial curve. This curve is shownby a dashed line in both figures, for an averageresult of 0.75 and 0.71 respectively. It can be seenthat the full curve in fig. 6 follows very roughly thebino:m.ial distribution. On the extreme right theobserved cu~ve lies somewhat above the binomialcurve. This means that a group of persons had amore than average power of discrimination andgave the right answer relatively often. On the otherhand there is a large group that' often heard nodifference at all and a small group that systematicallygave the wrong answers. A more detailed analysisleads to the conclusion that for the persons individu-ally the chance of giving a correct answer variesbetween 0.55 and 0.95.

The much greater disagreement between thecurves for question II is doubtless attributable tothe fact that, to answer. this question correctly,considerable familiarity with the sounds of musicalinstruments is required, a familiarity which can, .on the whole, only be expected of professional andamateur musicians. The curve in fig. 7 lies, at theleft, appreciably above the binomial, which meansthat a number of persons did indeed notice adifference, but systematically took the reproduetionto be the live music, and eonversely.

It might be objected that the foregoing conclu-sions are drawn from tests made with only a smallensemble and therefore may not be extended out-of-hand to apply to a large orchestra, because itsdynamic range is so much larger and consequentlymore difficult to deal with. In a subsequent articlewe shall discuss experiments in which a large orches-tra was involved - although, it may be added, thepurpose of the experiments was not to reproduceth~ music in another hall, but to improve the'acoustics of the hall in which the orchestra was.playing. On this occasion recording and reproduc-tion were again stereophonic. No systematic inquirywas held on the results, so that no figures can beoffered, but the ,opinion of the listeners gave us rheimpression that this reproduetion too was deceptive-ly like the real thing. We therefore feel justified inconcluding that it is possible to keep the imperfec-trions of electro-acoustical equipment at such a lowlevel as to make them almost imperceptible, even inthe case of a large orchestra.

Summary. The author poses the question: why, in spite of thetechnical progress made in electro-ucoustics, is there still anaudible difference between the music played in the concerthall and its reproduetion via a loudspeaker. The answer shouldnot be sought in the first place in minor technical imperfections,

hut rather in the two followingfacts: 1) the instruments of theorchestra are not heard separated because the sound emergesfrom the small opening of one loudspeaker, and 2) the roomwhere the music is reproduced is often acoustically inadequate.

As has long been known, the first drawback can be remediedby stereophonic reproduction: the sound is picked up by twomicrophones - preferably placed on an artificial head - andis reproduced, via separate channels, by at least two loud-speakers.To ascertain in how far stereophonic reproduetion can he

distinguished from "live" music, comparative tests werecarried out, in which strict vigilance was exercised to ensurethat the persons taking part in the tests (more than 300) weregiven no clue as to whether they were listening to "live"music (a small ensemble, concealed from view) or to a stereo-phonic reproduetion thereof. Ten tests were made per sessionand, for each test, the participants had to give written answersto two questions. Question I concerned the ability to discrimi-nate between the "live" music and the imitation, and question11 the "naturalness" of the music. The answers were treatedstatistically. The general conclusion reached is that, of theaverage of 75 correct answers out of a 100, 50 are attributableto discernment of the difference and 25 to guessing. Relativelyfew people (16%) can identify the difference with certainty,however, and then only with difficulty.. A postscript to this article reports on similar experimentscarried out in the Amsterdam Concertgebouw and in the"Academisch Genootschap" building in Eindhoven.

Postscript. After the above article had been prepared, twosomewhat differently arranged demonstrations with "live"and reproduced music weremade, on the instigation of G. Slotand with the cooperation ofthe Apparatus Division's AcousticalDevelopment Laboratory, in tlie "Kleine Zaal" (SmallAuditorium) of the Amsterdam Concertgebouw and in the"Academisch Genootschap" building at Eindhoven.As gramophone music was also involved in the demonstra-

tions, no stereophony was employed, but an attempt was madeby means of a specific arrangement of. the loudspeakers tocreate the best possible impression of auditory perspective.The installation comprised a type EL 3500 tape recorder (tapespeed 76 cm/s), a 60 W amplifier of very high quality and twoAD 5002loudspeaker sets. Each of these sets consisted of anacoustical box with two 9720loudspeakers (diameter 21 cm) forthe frequency range from 30 to 400 cts, and two high-noteprojectors, each equipped 'with one 97101\1loudspeaker, forthe frequency range from 400 to 20 000 cts.

For.certain pieces, a mixture was played of direct 'and repro-duced music. There was, for example, a piano-piece for fourhands, one part of which had been previously recorded andwas reproduced while the other was actually being played .Then there was the "farewell" piece, which had been recordedin such a way that the musicians were able to leave the plat-form one by one during the performance, while the music went'on without interruption. They did this, not as soon as their \part had been taken over by the reproduction, but some barslater, making sham movements in the meantime. It appearedthat the audience found it almost impossible to indicate withcertainty the moment of take-over.

In the "Academisch Genootschap" building at Eindhovenan enquiry was held after the interval, which is briefly reportedhere. Four pieces were played by a small ensemble, of which oneor two of the instruments had heen previously recorded.The non-playing musicians again made sham movements andthe hall was in partial darkness. The persons present wererequested after each number to indicate on a questionnaire foreach instrument whether they believed it had actually beenplaying or whethèr it had been reproduced.

DECEMBER 1955 REPRODUCED AND "LIVE" MUSIC 177

, Whe~ judging the results given below it should be bornein mind that, as the reproduetion was not stereophonic, someclues were given by the different directions from which thesounds of the musical instruments and of the loudspeakersreached the audience, In the front half of the hall especially,this factor was by no means negligible.

Out of an audience of 130 persons, 107 completed question-naires were returned. -The total number of wrong answersamounted to 378. If the 107 persons had only guessed, thenumber of wrong answers would have been 720. We set outbelow the results compiled for the instruments individually.Double bass. With the low notes produced by this instrumentit is very difficult to discern the direction from which thesound originates, so that the results in this casegive the fairestpicture of the quality of reproduction. It is therefore notsurprising that the largest number of wrong answers, viz.150,were returned for the double bass. In the following table, theactual figures are set out in the column headed "In reality",and the figures based on pure chance are given in the columnheaded" If guesswork". It can be seen that the differences areslight, so that we may assume that the audience was mainlyguessing.

I In reality I IfguessworkBass taken for reproduetion . .Reproduetion taken for bass . .Reproduetion recognized as such

618918

549018

Piano. For the piano, 74 wrong answers were returned. In thefollowing table we give an additional column headed: "If halfguessed"; the figures shown in this column, which Ure veryclose to the actual figures, would apply if half the audience hadonly guessed.

In reality If guess- If halfwork guessed

Piano taken for reproduo- Ition 27 63 27Reproduction taken forpiano. 47 84 45

Reproduetion recognized assuch . '. 60 21 62

Accordeon. The number of wrong answers given for theaccordeon was 62, against 74 for the piano. The distributionwas approximately the same as for the piano.Saxophone. Only 48 wrong answers were returned for thesaxophone. There is reason to believe that the recording wasnot so good as it might have been. Later tests have in factconfirmed this, showing that in this case a great deal dependedupon the positioning of the microphone 6).Percussion instruments. Although the directional effect asregards cymbals and brushes was very distinct, there werenevertheless 44 wrong answers.Only three out of 130 persons returned a fully correct

questionnaire. Itmay be assumed that the 23 persons whofailed to hand in a questionnaire were unable to discern anydifference, so that the actual result was probably even betterthan emerges from the above figures.An interesting detail worth mentioning in conclusion is

that the average number of wrong answers given by the 42. active music-Iovers present amounted to 3.0, as against 3.8given by the 65 others. No difference worth mentioning couldbe ascertained between the answers given by the technical.(mainly radio and sound engineers) and non-technical membersof the audience.

G) In the high register, the saxophone has a very pronounceddirectional effect, See H. F. Olson, Musical Engineering(Mc. Graw Hill, New York 1952), page 234.