Sculpting musical sound

David N LeePerception-Movement-Action Research Centre

University of Edinburgh

Talk given atShaping Music in Performance Workshop

King’s College, London10-11 March 2010

Summary of talk

A theory of action controland

applications to understandingmoving

andmaking music

Action-gaps

• Acting requires controlling action-gaps between current state and goal state

• Controlling action-gaps requires prospective sensory and intrinsic information

Multiple action gaps

• Acting generally requires controlling several action-gaps contemporaneously

τ• The principal informational variable for

controlling action-gaps is τ• τ is the time-to-closure (or the time-from-

closure) of an action-gap at the current rate of closing (or opening)

• τ of action-gap, X, equals X / &X

Properties of τ

• Action-time variable• Prospective informational variable• Universal variable• Directly perceptible

τ-coupling

• Foundation for controlling action gaps

• Means the ratio of the τ s of two gaps is constant

τ can be directly sensed through τ-coupling

Intrinsic guiding gaps

• Should be simple and sufficient• Should be rooted in ecological physics

(a)

How a gap changes undertauG - guidance

TauG-guidance parameters

K = ‘oomph’ A = amplitudeT = duration

tauG ‘kinetic melodies’ in the nervous system

Examples of tauG guidance

m-g

m-g

TauG-guidance of sucking in neonates

-10

-8

-6

-4

-2

0

-5 -4 -3 -2 -1 0

TauG

TauA

60

65

70

75

80

-10

0

10

20

30

40

50

60

13.4 13.6 13.8 14 14.2 14.4

wrist position (longitudinal axis; cm)

velocity of wrist (cm/s)

wrist position (longitudinal axis; cm)

velocity of wrist (cm/s)

time (s)

start

end

One day old infant gesture

TauG-guidance of pitch-glide singing

Va---ne

1 s

pitch (Hz)

TauG-guidance of attacking intensity- glide when bowing

Future directions

We have shown how, at the few hundred millisecond level, the shape of a musical sound (pitch and intensity glides) mirrors the shape of the movement that produces it. Both follow the same tauG mathematical formula. We are now moving in two new directions: to the sub-millisecond level to explore how sound waves are sculpted to generate the timbre or quality of sound, and to the supra-second level to explore how the shapes of musical phrases are sculpted. Preliminary results suggest that tauG also features at these two levels.

References

Schogler, B., Pepping, G-J. & Lee, D. N. (2008). TauG-guidance of transients in expressive musical performance. Experimental Brain Research, 198, 361-372.

Lee, D. N., & Schogler, B. (2009). Tau in musical expression. In S. Malloch & C. Trevarthen (Eds.), Communicative Musicality: Exploring the basis of human companionship. Oxford: Oxford U. P.

Lee, D. N. (2009). General Tau Theory: evolution to date. Special Issue: Landmarks in Perception. Perception, 38, 837-858.