Slide 1BeatSlide 3Expectations and Tapping experimentsExpectancy of next beatTapping experimentsTime shrinkingSlide 8Subjective durationGroupingsNecklace NotationNecklace NotationNumerical NotationsMIDI event data MIDI = Musical Instrument Digital Interface)Tabla TalasScience of TablaHierarchy of levelsMeasures/Beats/TatumsMicrotiming measurements for a SambaMicrotiming VariationsBar Wrapping Visualization of MeterMusicianship in timingRubatoOnsetsAlgorithms for Finding OnsetsFinding meter and tempoMusicianship in rhythmHacking a recording to change meterRemake atrociousCharacter of song can remain despite large timbre changesRhythm and Meter Note Perception of groupings Mike Oldfield, Tubular bells, theme song for the ExorcistBeat•Beat – underlying even pulse common in many types of music•Range typical of that given on a metronome -frequency 30 to 200 beats/minute OR 0.5-4 Hz -periods between 250ms and few seconds.-For clicks closer together than 100 ms, they run together.-Separated longer than a few seconds we don’t feel that they are associated-same range as sung vibratro or tremolo, or heartbeat-beats we feel are slower than frequencies we hear•We tend to move spontaneously to the beat. •Newborn babies respond to the beat (e.g. Winkler et al. 2009 – recent press on this, as seen from electric signals picked up near the brain).Areas of the brain (as seen by fMRI (functional magneto resonance imaging) respond to regular beatsGrahn & Brett (2007), Journal Cognitive Science 19:5, 893Expectations and Tapping experiments•First listen.•Then everybody tap after the sound file ends•This is the first beat pattern in the next figure and based on one of Dessain’s experimentsExpectancy of next beatPeter Dessain, Music Perception: An Interdisciplinary Journal, Vol. 9, No. 4 (1992), pp. 439- 454tapping experimentsTapping experimentsDessain 92Time shrinking •Duration of short time intervals is conspicuously underestimated if they are preceded by shorter neighboring time intervals.Figure by Petra Wagner and Andreas WindmannSound clip from http://listverse.com/2008/02/29/top-10-incredible-sound-illusions/Subjective durationFigure from Psychoacoustics by Zwicker and FastlNote decaying envelopes are not heard as they are equivalent to echoes and so are suppressed. Because of this we would have expected that the flat top would be half the interval for the perception of 1/8th note. But this is not the case.GroupingsImages and three sound clips from W. Sethares book on Rhythm and Transformwith different timbres19/20Necklace NotationImages and clips from Rhythm and Transform by W. SetharesWith different timbre emphasis the perceived starting position variesNecklace NotationImages and clips from Rhythm and Transform by W. SetharesNumerical NotationsImage and clip from Rhythm and Transform by W. SetharesMIDI event data MIDI = Musical Instrument Digital Interface) MIDI DATACHANNEL TIME NOTE DURATION VELOCITYMeasures beat ticks beats+ticks velocity/off1 4:3:0 F2 1:100 100:64A certain number of ticks makes up each beatimage from audacityTablaTalasImage from http://www.chandrakantha.com/tablasite/quick.htmScience of TablaImage and clip from http://www.chandrakantha.com/tala_taal/jhoomra/jhumra.htmlFigure From Rhythm and Transforms by W. SetharesJhumraHierarchy of levelsDavid Rosenthal, Computer Music Journal, Vol. 16, No. 1 (1992), pp. 64-76Measures/Beats/Tatums•Measures: groupings of beats, repeatingCyclic pattern of rhythm if repetitive•Beats: underlying pulse•Tatums or Ticks. Small unit of time. Beats and note onsets are described in units of tatums from the beginning of measure or cycleAbove is an example of a hierarchy•Classification of a series of onsets into a type of rhythm based on minimizing the complexity of the required hierarchy or minimizing the syncopation.Microtiming measurements for a SambaWhile we might perceive a rhythm in terms of regular intervals, however musicians may with systematic small deviations from calculated intervals/durations Fabien Gouyon, SBCM 2007 proceedingsMicrotiming VariationsFabien Gouyon, SBCM 2007 proceedings systematic shifts in timing of order 20ms associated with musicianship and musical style/genreBar Wrapping Visualization of MeterMatthew Wright et al. 08ISMIR 2008 – Session 5c Tempo is varyingBeat identification done in softwareMicrotiming variations then shown in this waytempotimeMusicianship in timingNote double hits by bass Percy JonesDifferences in timing of bass compared to drum make each instrument stand out yet rhythm is still strongRubato•Harpsichord and rubato,•someday a good clip will illustrate this!OnsetsOpposite of synthesis Groups of overtones moving together appear as one soundFast clicks appear as one element Any factors that can create auditory boundaries can create patterns in time that can be perceived as rhythmic (following Sethares’s statement in 4.3.8).-- Boundaries = Quick Variations in timbre, pitch or loudnessAlgorithms for Finding OnsetsCan be referred to as Feature vectors•Reduce sampling rate•Partition into frequency bands•Search for variations in total energy (volume) spectral mean or center, spectral dispersion or large variations in energy in any particular band•Software developed such as beatroot outputs a MIDI event file of onsets•With beatroot you can adjust location of individual onsets and add or remove themFinding meter and tempo•For tempo:–Autocorrelation or Fourier methods (J. Brown)–Periodicity transforms (Sethares)•These fail if the tempo is varying–Adaptive oscillators work if tempo varies smoothly–Perceptive idea of “internal clock”•Hierarchy of levels to identify meter (Rosenthal)•Minimization of number of syncopations (Longuet-Higgens & Lee 84)•Statistical models•If you have a score or a MIDI file then synching the sound file may be more straightforward•My impression is that this is an active area of researchMusicianship in rhythmNot captured by simple descriptions or classifications of rhythms: -meter changes, accent changes-accelerandos and ritardos (tempo variations)-microtiming variations Delays or jumps shifting the entire beat, bending timeDisplacements, delays or jump in onsets that don’t change the beat-timbre variations --- different types of sounds (like different drums) substituted -omissions, doublings of strokes-graces notes added-rhythm pattern reset (shifted?) or variedHacking a recording to change