Spectral properties of rhythm performance

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Spectral propertiesof rhythm performance

• Carl Haakon Waadeland
• Department of Music
• Norwegian University of Science and Technology
  (NTNU)
• Trondheim
• E-mail carl.haakon.waadeland_at_hf.ntnu.no

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Introduction

• Basic axiom
• Performance and experience of rhythm is
  intimately related to movements of the body
• Focus of investigation
• To study possible relations between
• movement characteristics (or movement
  categories) and
• rhythmic expression (expressive timing)

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• .underlying this approach
• we regard a musicians various ways of moving
  when playing an instrument as an expression of
  timbral aspects of rhythm..

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A theoretical model

• (C.H.Waadeland, JNMR, 30(1), 2001)
• Idea
• Rhythm performance is regarded as result of
• atomic movements interacting with each other.
• sinusoidal movements frequency modulation

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• Example
• Swing groove in jazz

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• Example
• Swing groove in jazz
• MIDI recording, quantized in triplets
• (Computer implementation by Sigurd Saue, NTNU)

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• Swing in sixteenth notes
• A frequency modulation of a)

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• Swing in eighth notes
• Another frequency modulation of a)

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• Conclusion
• Various applications of FM to movement curves
  yield approximations to live performances of
  rhythm (swing/Vienna waltz/springar in
  Norwegian folk music)
• But
• This model is based on theoretical movements (FM
  of sinusoidals)
• What do the real movements look like?

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Empirical investigations of jazz drummers
movements

• (C.H.Waadeland, 2001 ?)
• General question
• What can studies of a jazz drummers movements
  tell us about the way the drummer is performing
  swing grooves ?

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• Subjects
• Jazz drummers, students and teachers at Dept. of
  Music, NTNU section of jazz education.
• Task
• Play swing groove restricted to various
  performance conditions.

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• Aim
• Study possible relations between the drummers
  movements and the following performance
  parameters
• Tempo
• Dynamics
• Swing ratio (rhythmic subdivision)

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Method/Equipment for Measuremets

• (Measurements assisted by Geir Oterhals,
• Section of Movement Science, NTNU)

Cameras (6) transmitting infra red light
Force plate measuring force from drumstick
Markers (5) reflecting the light
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• The following equipment is used
• 6 cameras (Proreflex camera system) are used to
  measure movements of the arm and the drumstick
  (kinematics). Sampling rate 240 Hz
• A force plate (Kistler) is used to give accurate
  measurements of attack points and musical
  dynamics. Sampling rate 960 Hz
• A minidisk is used for audio recording of the
  experiment

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What do the measurements look like ?

• A short animation of a performance of swing

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• A graphic representation of a performance of
  swing (height vs. time)
• Wrist Hand Drumstick

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Analytical approach

• A method of analysis which seems to give
  interesting information related to connections
  between movement patterns and rhythmic phrasing,
  is spectral analysis of swing performance.
• By this method the sinusoidal components of the
  movement patterns are detected.
• The analysis is done by using Matlab calculating
  FFT (Fast Fourier Transform).

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• Example Count-in tempo 90bpm, subdivision in
  triplets

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Speculative thoughts

• The measurements illustrate different movement
  patterns related to differences in tempo,
  accentuation and rhythmic subdivision
• The spectral approach suggests alternative ways
  of constructing models of rhythm production

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• a) Additive synthesis
• Adding sinusoidal movement curves to
• obtain approximations to movements
• of rhythm performance

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• b) Applying frequency modulation
• FM Wave shaping
• Metronomic Modulated Movement
• movement movement curves
• curves, curves through approximating
• representing attack points movements of
• note values approximating rhythm
• rhythm performance
• performance
• New model of rhythm performance?