Creating a Hardware Granular Synth

8/18/2019 Creating a Hardware Granular Synth

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University of Derby

Faculty of Arts, Design and Technology

Creating a hardware granular synthesizer

Author

Vladimir Coman-Popescu

upervisor

Dr! "ruce #iggins

Academic $ear %&'% ( %&')

ubmitted in support of a degree in

*A *usic Production

'


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AbstractThe follo+ing report deals +ith the e periment of creating a hard+are granular synthesi er +ith the

purpose of assessing +hether the techni.ue has the potential of becoming accessible to musiciansoutside of the computer music area, as +ell as +ith the author/s personal motives and e plorationsof granular synthesis for this purpose! After establishing the rationale behind the e periment andma0ing predictions about the pro1ect/s success, a short revie+ of relevant literature on the sub1ect isundergone, for conte t, and a better understanding of the types of granular synthesis and currentavailable tools that handle it, before a detailed description of the design and build processes isoffered, as +ell as an evaluative approach to e amining the finished instrument and asserting thee periment/s success! 2n closing, further avenues for future improvement of the design and technicalspecifications are suggested!

Table of Contents

1. Introduction

a! 3ranular synthesis in a nutshell

b! 4ationale

c! The plan

%! Granular synthesis over time, tools and theory

a! 5iterature 4evie+ - A hort 6istory

- Theory and Types

b! 3ranular synthesis tools available

3. Building the Grainscape

a! Finding the Design b! The "uild Process

4. Issues, Achievements and Room for Improvement

5. References

. Appendi! " internet lin#s

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Introduction

Granular Synthesis in a nutshell

7ut of the multitude of techni.ues for sound creation and manipulation available through the useof technology at this time, granular synthesis is considered by some to be one of the most po+erful8Price, %&&9:!

"ased on physicist Dennis 3abor/s idea about the .uantum of sound, proposed in his ';Acoustical .uanta and the theory of hearing ?, granular synthesis +as first suggested as a computermusic techni.ue for producing comple sounds by 2annis @ena0is and Curtis 4oads 8Trua , %&'&:!

The main principle of granular synthesis is the division of sound into multiple very small slices, or>grains?, +hich are then played bac0 repeatedly to produce a continuous sound, and using the pitch,si e or other properties of these grains to achieve a significant number of possible sonic results! Forinstance, this techni.ue is used to sever the connection bet+een the pitch and duration of soundrecordings, thus offering the possibility of changing a sound/s pitch +ithout affecting its durationand vice-versa! #hile a lot of the granular synthesis soft+are instruments available today are basedon sampling recorded sound and slicing it into grains +hich can then be played bac0 +hile varyingtheir source position from +ithin the overall sound recording, sound grains can be 1ust as +ellgenerated by mathematical functions! Another e ample, an arguably more artistic use of thegranular synthesis techni.ue is randomi ing the scrub of each grain being played bac0 in order to

produce a completely ne+ sound te ture +ith a number of musical performance and sound designapplications!

Rationale

Although part of the applications of +hat is no+ named granular synthesis +ere achieved to acertain degree +ith hard+are relatively soon after its theori ation in the form of tools such as Pierre

chaeffer/s and ac.ues Poullin/s Phonogene 8Poullin, ';9


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musicians outside of the electronic music scene or academia circles became an important interestfor me! 2 believe that its versatility in producing a +ide range of sounds should be 0no+n by anumber of people e.ual to those 0no+ing ho+ to t+ea0 the B on a mi er, the Tone 0nob on anelectric guitar or the 3ain 0nob on a distortion pedal! 2 believe that as music evolves over the yearsand more tools are available to musically creative individuals, so should the accessibility to and0no+ledge about these tools gro+ along +ith them!

Therefore, the purpose of this pro1ect is to e plore the possible accessibility of this techni.ue andfind out as closely as possible ho+ accessible granular synthesis can be +hen implemented on ahard+are platform, from a technical standpoint! This can be investigated by creating a hard+aregranular synthesi er ideally aimed at musicians and individuals that don/t label themselves ascomputer-music-literate! For the sa0e of clarity throughout this paper, as +ell as for the love ofnomenclature, this particular granular synthesi er +ill be called the 3rainscape!

Also for the sa0e of absolute clarity, the research .uestion being e plored is

6o+ technically accessible can granular synthesis be as a musical approach +hen implemented ona hard+are platformE

The plan

2/ve previously dealt +ith the concept of creating a hard+are granular synthesi er in a student paper submitted for the 4esearch *ethods module in December %&'%! As such, 2 found itappropriate to use some of the te t material from that particular paper in this section of the report,as the concepts and their argumentation used in that conte t are highly relevant to the sub1ectapproached in this one!

#hen considering the research .uestion posed previously, there is a possibility that confusions can

arise regarding the terms >accessible? and >hard+are platform?! 2n order to ma0e the research aimsas clear as possible, the t+o terms must clearly be defined in the conte t of the design and buildstages about to be undergone!

>Accessible?, in this case, references t+o elements the budget allocated to the resources used tocreate the 3rainscape 8or price range of the instrument:, and its ultimate ease of use +hen it scompleted!

At this stage in development, estimating a price range for the instrument itself as if it +ere meantfor mass production +ouldn/t be practical! The current pro1ect focuses more on the technical aspectsthat need to be resolved, rather than problems related to the current electronic instrument mar0et, asthe limited time allocated to this pro1ect couldn/t allo+ for effective mar0et research and other non-

technical issues! 6o+ever, a a good indicator of its possible accessibility in terms of price is themoney spent on the resources used to create the 3rainscape! 2n this case, my aim is the arbitrarysum of '9&G, if for no other reason than the fact that that/s the money 2/d personally be inclined tospend on a synthesi er should 2 someho+ be put in a position +here 2/d be obligated to do it!

The definition of the term >ease of use? implies that the instrument should pose no difficulties tothe average user, and be of the 8in layman terms: >plug-and-play? variety!

"ut +hat is >Plug-and(play?E For that matter, +hat is ease of useE Again, due to time constraints posed by the one-year of full time study conte t, creating a survey aimed at various musicians,implementing it, interpreting the results and them implementing these interpretations into theinterface of the instrument might end up ta0ing a+ay too much time from the .uantitative research

phases, platform testing, design and build stages!Therefore, 2/ve formed a sub1ective, yet simple definition of >ease of use?! For the purpose of this

pro1ect, this +ill mean no more than ) button presses bet+een plugging the instrument in and


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hearing the first sound, no s+itching bet+een pages and ban0s of controls, and no more than onefunction for each button, 0nob, slider or other means of human interfacing on the front panel of theinstrument! This is, of course, a completely sub1ective vie+ of >ease of use? and is by no meansconsidered a universal definition of the term +hen it comes to instrument design and construction!

The term >hard+are? is also used fairly loosely! "ecause of the price range mentioned earlier, as+ell as the rigid time constraints, implementing granular synthesis on an analogue platform is note pected to be the approach chosen to create the instrument at the end of the design andconstruction stages! Therefore, microcomputers running open source soft+are are e pected to be thesolution found for the implementation of granular synthesis!

This implementation contains both hard+are and soft+are elements, but it +ill be considered asfalling under the definition of a >hard+are? approach for the purpose of this 2ndependent

cholarship, since the user does not interface +ith the soft+are via a display, and the final versionof the instrument +ill have the microcomputer do nothing else besides sound generation throughgranular synthesis!

As a result of this reasoning, there +ill be t+o purposes to the 3rainscape, in this case, the first being finding out ho+ cheaply and accessibly a hard+are granular synthesi er can be built! 2f theresulting tool is deemed functional and potentially useful from a musician/s standpoint, testing thisfirst aspect has the potential of provo0ing further research in this area and ultimately influencing theelectronic musical instrument mar0et some time in the foreseeable future! The second purpose is toe plore the functionality achievable +ith such lo+-cost means and produce a general idea about thefeasibility of such a design based on soft+are and microcomputers!

As a short aside, my personal predictions at the start of this pro1ect are that this design is thestarting point of a genuinely enlightening e ploration into the possibilities of electronic instrumentdesign, and that the 3rainscape pro1ect created at the end of it can at least prove that granularsynthesis is achievable on platforms outside of the computer music area!

Therefore, the electronic instrument +ill be a practical proof-of-concept that/s accompanied by acomplete brea0do+n of the design and build processes, as +ell as an evaluative appraisal of itsabilities, advantages and fla+s and proposed methods of improving upon the approach testedherein!

8Coman ( Popescu, %&'%:

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Granular synthesis over time, tools and theory

Literature review

A Short History

“In dense portions of the Milky way, stellar images appear to overlap, giving the effect of a near-continuous sheet of light... The effect is a grand illustion. In reality... the nighttime sky isremarkably empty. Of the volume of space, only one part in !"# is filled with stars.$

8Haler ';;=:

The above .uote is used my Curtis 4oads in his %&&' boo0 >*icrosound? as a parallel to the +ayhumans perceive clouds of sound as a single auditory event +hile also using the e ample of a seriesof impulses repeated at a rate of %& 6 to be heard as a single, continuous tone!

This parallel and subse.uent e ample are a perfect e planation of the basis of granular synthesisand ho+ sound te tures and other sonic events can be created by manipulating s+arms of >grains?8or atoms: of sound!

The notion that all matter is made out of small individual elements goes bac0 as far as the 9 th

century "C, +hen philosophers Democritus and 5eucippus posed forth the idea of atoms,indivisible particles out of +hich both matter and energy are composed of along +ith empty space!8"arnias, %&&


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Theory

There are t+o basic approaches to granular synthesis

The first approach involves analysing an e isting sound recording and then resynthesi ing selectedgrains to generate a ne+ sound! 2n this approach, grains are slices or selections of the recordedsound being used!

The second approach involves generation of sound grains through computer algorithms anddoesn/t involve any analysis stage or pre-recorded sound! 8"arnias, %&&


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Building The Grainsca e

Finding the Design

#or0 on building the 3rainscape commenced by testing the granular synthesis capabilities of aseries of soft+are tools, to try and determine the type of functionality 2 +anted to achieve ande plore +ith the hard+are about to be built! At this stage, 2 set my sights on trying to ans+er thefollo+ing t+o .uestions

#hat should the 3rainscape actually do in terms of functionalityE

and

#ould 2 personally be inclined to use it outside of a computer music environmentE

As previously mentioned, D P algorithms based on granular synthesis are the basis of any toolsdealing +ith time stretching or compressing audio clips +ithout altering pitch, so 2 first set out toinvestigate the +ay that DA#s such as Pro Tools from Avid and Ableton 5ive deal +ith +arpingaudio! Although 2 discovered a multitude of +hat 2 considered to be creative uses for this type ofaudio +arping, 2 ultimately concluded that 2 personally +ouldn/t be inclined use this type offunctionality outside of a studio production situation!

2 then spent a considerable amount of time e perimenting +ith different types of plugins thatsupported granular synthesis in Ableton 5ive, up to and including 5ive/s native >3ranular Delay?device, as +ell as trying out patches built in the visual programming environments *a andPureData, that dealt +ith granular synthesis! Bventually, 2 decided that the most spectacular andversatile tool out of all the soft+are 2 tested +as a *a -based device designed by 4obert 6en0ea!0!a! *onola0e, called the 3ranulator! 2ts functionality includes real-time recording of audio,typical AD 4 controls, grain position randomi ation and the option of selecting the number ofvoices, as +ell as more advanced features li0e the option of applying amplitude modulation orfre.uency modulation to the grains, per-grain amplitude curve, a > can? control, allo+ing the grain

position to move progressively for+ard over the selected audio snippet and an assignable 5F7!86en0e, %&'):

2 decided to try to achieve part of the functionality of the 3ranulator for my 3rainscape tool, +hilealso trying to simplify it to a certain degree, both for the sa0e of efficient time allocation and

because of the 3ranulator/s inherent *a -based modular nature ( once the basic features areimplemented, it is possible to add more functionality +ithout having to start everything again fromthe ground up! Also, less initial features +ould ma0e its basic functionality easier to master!

The 3rainscape +ould have the follo+ing functionality the user +ould record a fe+ seconds ofaudio into an audio buffer via a microphone or 4CAKphono input, +hich could then be played bac0+ith the 0eys on a *2D2 controller and looped immediately, similar to a regular sampler! The usercould then ad1ust the si e of the looped section of audio 8or >grain?: and it/s position +ithin theaudio buffer, as +ell as having typical Attac0, Decay, ustain and 4elease controls! Anotherfunction +ould be a 0nob controlling the rate of randomi ation of the position of the grain, relativeto the position initially set by the user! A shorter and more accessible e planation +ould be that a

performer could sing into the 3rainscape and then create lush, spacious soundscapes or harshgranular stretches out of +hat they recorded, thus achieving a form of .uasi-synchronous granular

synthesis!#ith this in mind, 2 started loo0ing for a platform suitable for implementing the 3rainscape patch

on! After a some+hat lengthy process of finding a number of hard+are manufacturers, ruling some

L


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of them out, corresponding +ith the rest and establishing endorsement connections and support, 2finally received t+o platforms for the purpose of testing the creation of the 3rainscape a 4aspberyPi microcomputer and a Cubo microcomputer! The selection and correspondence process is notcovered here on account of it not being directly tied to the granular tool being built and assessed as

part of this pro1ect!

After receiving the 4aspberry Pi and the Cubo , 2 started testing the both of them to see ho+ theyhandle sound-based applications! Unfortunately, upon a closer e amination, 2 found that the more

po+erful Cubo apparently +asn/t designed for handling audio, and either the process of installingthe operating system on it +as beyond my grasp, or the unit 2 received +as corrupted! This left me+ith the single options of using the less po+erful 4aspberry Pi! 6o+ever, in contrast to the verycomplicated-to-set-up 8and potentially inaccessible: Cubo , the 4aspberry Pi +as designed forchildren to learn programming! 84aspberry Pi FA , %&'%: and it came +ith a pre-installed versionof the operating system on an D card! After ma0ing sure it could output audio files, 2 advanced tothe soft+are design stage!

*y initial plan +as building a *a patch based on 4obert 6en0e/s 3ranulator and implementing itonto the 4aspberry Pi! 6o+ever, since the 4aspbian operating system on the Pi is based on 5inu

84aspberry Pi FA , %&'%: and *a isn/t available for 5inu 8*a FA :, the only other solutionthat 2 found +as to replace *a +ith a very similar visual programming environment calledPureData 8also referred to as Pd:! Although 2 +as confident 2 +ould be able to learn Pd in time tocreate the 3rainscape, 2 discovered that in spite of their similarities 8both are ob1ect-based graphical

programming environments: the differences in approaching certain functionalities bet+een *a andPd are .uite substantial and that the method of achieving granular synthesis used in the 3ranulator*a patch that inspired me +as in no +ay valid +hen it came to Pd! The solution +as to find adifferent method, based on Pd, to achieve the same functionality that 2 +as after!

The Build ProcessAfter several +ee0s of e ploring Pd and learning its .uir0s and possible approaches, 2 managed to

create a patch that very closely achieved +hat 2 had in mind!

;

Illustration


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$o% it %or#s

2n Pd, audio can be recorded as point values in graphical representation called an Array! endinginteger number values to that array plays bac0 the point corresponding to each number it receives!Point values 8in this case used as digital audio samples: can be +ritten to the array +ith thetab+riteM ob1ect, and a tabread


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to the user-set start position 8>spray?:!

Therefore, each >voicevoicevoice? abstraction represents a single synthesi er voice! 2 had settledearly on on creating a polyphonic synthesi er, so 2 implemented < of these abstractions in order toma0e a adsr? abstraction that applies a volume envelope for each of the>voicevoicevoice? patches!

The relationships bet+een all of these ob1ects is visible in 2llustrations ', % and ), as +ell as the patch being documented on the 3rainscape blog and available for do+nload! All lin0s included inthe Appendi !

#ith the patch completed, there still remained the problem of accessing it on the 4aspberry Pi+ithout the need of using a monitor, the 3raphic User 2nterface, a mouse and a computer 0eyboard!The patch +ould need to launch automatically as soon as the microcomputer is plugged in, 1ust li0ethe functionality of any hard+are tool is available as soon as it/s turned on!

This +as achieved by combining a set of soft+are functions in both Pd and the 4aspberry Pi7perating ystem itself, as 2 had no 0no+ledge of creating Python scripts, +hich +ould have beenan alternative solution! Pd +as set to run the 3rainscape patch at launch, +hile the patch itself had a>loadbang? ob1ect triggering a message to the soft+are itself turning on the D P algorithm! Pd +asalso set to start automatically +hen the 4aspberry Pi +as plugged in, by having the Pi s0ip thenormally obligatory login and launch the graphical user interface, +here an >autolaunch? 5inufolder +as set up containing a shortcut to the Pd soft+are!

The physical side of the design +as resolved by integrating both the 4aspberry Pi and the audiointerface into the generously-spaced casing of a


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Issues, Achievements and !oom for Im rovement

After several tests, the current iteration of the 3rainscape unveiled a series of problems that need

to be resolved in order to move the platform to+ards being a viable option for e pandingaccessibility to the granular synthesis techni.ue!

The main issue is audio .uality! 2/ve discovered that based on the transformerKcharger being usedto provide po+er to the 4aspberry Pi significantly affects the output audio! #hile there are nodigital artefacts, there is constant regular clic0ing that never completely disappears regardless of thetransformer used!

The second problem is latency, +hich occurs both +hen recording audio into the Array and bet+een pressing a 0ey and hearing the note it corresponds to!

To my 0no+ledge, both of these problems can be fi ed by properly calibrating the U " audiointerface being used! 7n the soft+are side, maybe a solution can be found to +or0 +ith drivers ore.uivalent soft+are in order to have full access to the performance of the interface! 2/m sure that asolution can be found to better integrate it +ith the 4aspberry Pi, and 2 +ill personally pursue itmyself in the future! 4egarding the clic0ing, 2/m also personally convinced this can be fi ed after athorough e amination of the hard+are 8both the interface and the 4aspberry Pi: by a person moreelectronically proficient than myself! The Appendi contains lin0s to a number of internet sourcesclaiming achievements in audio clarity +ith the 4aspberry Pi, +hich, although prove the potentialof the 3rainscape of evolving from a viable tool idea to a mar0etable instrument, 2 haven/t includedas references on account of their some+hat unofficial nature!

Despite these problems, ho+ever, this prototype 3rainscape is proof that granular synthesis isindeed possible on a platform that is very cheap compared to all other current solutions on the

mar0et, and easy to comprehend and use! The 3rainscape has been used successfully and +as easilyunderstood by a number of people +ith at least a marginal connection to the musical +orld, and thecomments 2 received from these tryouts ranged from >This is so a+esomeN? to >2 don/t li0e the noiseit ma0es, but 2 can easily get ho+ it +or0s?!

As a short aside, the 3rainscape is also proof of the potential of this platform to become muchmore than a host for accessible granular synthesis ( if this CPU-intensive sound techni.ue is

possible on the 4aspberry Pi, then surely a simpler PureData patch based on a less demandingsound generation or manipulation method li0e fre.uency modulation or e.uali ation can surely beachievedE This begs the .uestion about the possibility of creating a universal synthesi erKeffects

processor based on Pd and the Pi, +here the tool can become +hatever its user base can program inPureData! 6o+ever, regardless of the e citing nature of this idea, e periments in this direction arethe potential sub1ect of another report!

o, regarding the research .uestion posed at the beginning of this report, >6o+ accessible cangranular synthesis be +hen implemented on a hard+are platformE>

2f the definitions of ease of use and accessible budget that 2/ve given in beginning of the argumentare to be considered viable, and the central factors ta0en into consideration for the purpose of thisreport, the ans+er is that granular synthesis can become 1ust as accessible as any other currently

popular musical techni.ue or instrument! 3iven time and effort invested into development,something similar to the 3rainscape could potentially be produced and offer a very cheapalternative to conventional synthesi ers currently on the mar0et, and ma0e the sounds of granular

synthesis a household occurrence as +idespread as the electric guitar!

'%


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!eferences

'! imon Price - >3ranular ynthesis ( 6o+ 2t #or0s O #ays To Use 2t? - published in oundon ound in December of %&&9!

%! "arry Trua - >3ranular ynthesis? - http KK+++!sfu!caKMtrua Kgran!html, %&'&!

)! Curtis 4oads - >*icrosound? - *2T Press, %&&'!

*+apport des techni(uesd+enregistrement dans la fabrication de matieres et de formes musicales nouvelles applications la musi(ue concrete ?:! Ars onora, no! ;, ';9

9! 4obert 6en0e ( 3ranulator 22 http KKroberthen0e!comKtechnologyKgranulator!html , %&')!

J! 4aspberry Pi FA - http KK+++!raspberrypi!orgKfa.s , %&'%=! *a FA - http KKcycling=

L! Haler, ! >Cosmic Clouds!? Ie+ $or0 cientific American 5ibrary, ';;=

;! Dimitris "arnias >3ranular ynthesis?, sonicspace!org article, %&&<

'&! Dennis 3abor, >Acoustical .uanta and the theory of hearing? Iature, ';4esearch Plan Development?, University of Derby student paper, %&'%!

')

http://www.sfu.ca/~truax/gran.htmlhttp://www.ars-sonora.org/html/numeros/numero09/09f.htmhttp://www.ars-sonora.org/html/numeros/numero09/09f.htmhttp://roberthenke.com/technology/granulator.htmlhttp://roberthenke.com/technology/granulator.htmlhttp://www.raspberrypi.org/faqshttp://cycling74.com/support/faq_max6/http://www.ars-sonora.org/html/numeros/numero09/09f.htmhttp://www.ars-sonora.org/html/numeros/numero09/09f.htmhttp://roberthenke.com/technology/granulator.htmlhttp://www.raspberrypi.org/faqshttp://cycling74.com/support/faq_max6/http://www.sfu.ca/~truax/gran.html


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A endi"

The 3rainscape Pro1ect Diary blog - http KKgrainscape!+ordpress!comK

Audio 2ssues on the 4apberry Pi

http KKpuredata!infoKdocsKraspberry-pi

http KK+++!raspberrypi!orgKphp"")Kvie+topic!phpEfR)9OtR

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Creating a Hardware Granular Synth