Note Perception of groupings Mike Oldfield Tubular bells theme song for the Exorcist Beat Beat underlying even pulse common in many types of music Range typical of that given on a metronome ID: 172064
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Slide1
Rhythm and Meter
Note Perception of groupings
Mike Oldfield, Tubular bells, theme song for the ExorcistSlide2
Beat
Beat – underlying even pulse common in many types of musicRange typical of that given on a metronome
frequency 30 to 200 beats/minute OR 0.5-4 Hz p
eriods 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).Slide3
Areas of the brain (as seen by
fMRI (functional magneto resonance imaging) respond to regular beats
Grahn
& Brett (2007), Journal Cognitive Science 19:5, 893Slide4
Expectations and Tapping experiments
First listen.
Then everybody tap after the sound file endsThis is the first beat pattern in the next figure and based on one of Dessain’s experimentsSlide5
Expectancy of next beat
Peter
Dessain, Music Perception: An Interdisciplinary Journal, Vol. 9, No. 4
(1992), pp. 439- 454
tapping experimentsSlide6
Tapping experiments
Dessain
92 Slide7
Time shrinking
D
uration of short time intervals is conspicuously underestimated if they are preceded by shorter neighboring time intervals.
Figure by Petra Wagner and Andreas WindmannSlide8
Sound clip from
http://listverse.com/2008/02/29/top-10-incredible-sound-illusions/Slide9
Subjective duration
Figure from Psychoacoustics by
Zwicker and Fastl
Note 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 1/8
th
note. But this is not the case.
Slide10
Groupings
Images and three sound clips from W.
Sethares
book on Rhythm and Transform
with different timbres
19/20Slide11
Necklace Notation
Images and clips from Rhythm and Transform by W.
Sethares
With different timbre emphasis the perceived starting position variesSlide12
Necklace Notation
Images and clips from Rhythm and Transform by W.
SetharesSlide13
Numerical Notations
Image and clip from Rhythm and Transform by W.
SetharesSlide14
MIDI event data
MIDI =
Musical Instrument Digital Interface)
MIDI DATA
CHANNEL
TIME
NOTE
DURATION
VELOCITY
Measures
beat ticks
beats+ticks
velocity/off
1
4:3:0
F2
1:100
100:64
A certain number of ticks makes up each beat
image from audacitySlide15
Tabla
Talas
Image from http://www.chandrakantha.com/tablasite/quick.htmSlide16
Science of
Tabla
Image and clip from http://
www.chandrakantha.com/tala_taal/jhoomra/jhumra.html
Figure From Rhythm and Transforms by W.
Sethares
JhumraSlide17
Hierarchy of levels
David Rosenthal, Computer
Music Journal, Vol. 16, No. 1
(1992), pp. 64-76Slide18
Measures/Beats/Tatums
Measures: groupings of beats, repeating Cyclic pattern of rhythm if repetitive
Beats: underlying pulseTatums 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.Slide19
Microtiming measurements
for a Samba
While 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 proceedings Slide20
Microtiming Variations
Fabien
Gouyon, SBCM 2007 proceedings
systematic shifts in timing of order 20ms associated with musicianship and musical style/genreSlide21
Bar Wrapping Visualization of Meter
Matthew Wright et al. 08
ISMIR 2008 – Session 5c
Tempo is varying
Beat identification done in software
Microtiming
variations then shown in this way
tempo
timeSlide22
Musicianship in timing
Note double hits
by bass Percy
JonesDifferences in timing of bass compared to drum make each instrument stand out yet rhythm is still strongSlide23
Rubato
Harpsichord and rubato,someday a good clip will
illustrate this!Slide24
Onsets
Opposite of synthesis Groups of overtones moving together appear as one sound
Fast 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 loudnessSlide25
Algorithms for Finding Onsets
Can be referred to as Feature vectorsReduce sampling rate
Partition into frequency bandsSearch for variations in total energy (volume) spectral mean or center, spectral dispersion or large variations in energy in any particular bandSoftware developed such as beatroot outputs a MIDI event file of onsets
With beatroot you can adjust location of individual onsets and add or remove themSlide26
Finding meter and tempo
For tempo:Autocorrelation or Fourier methods (J. Brown)P
eriodicity transforms (Sethares)These fail if the tempo is varyingAdaptive oscillators work if tempo varies smoothlyPerceptive idea of “internal clock”
Hierarchy of levels to identify meter (Rosenthal)Minimization of number of syncopations (Longuet-Higgens & Lee 84)Statistical modelsIf 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 research
Slide27
Musicianship in rhythm
Not captured by simple descriptions or classifications of rhythms:
meter changes, accent changesaccelerandos and ritardos (tempo variations)
microtiming variations Delays or jumps shifting the entire beat,
bending time
Displacements, 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 variedSlide28
Hacking a recording to change meter
James Bond Theme Song by Monty Norman- arranged by John Barry and from the movie Dr. No
Bond Waltz - W.
Sethares
B
eat regularization or stretching for effect can be done in the studio, but software is not necessarily standardized or cheep.
Beat tracking allows interesting composition experiments (such as above)
-For other compositional ideas see
Sethare’s
sound clips in his bookSlide29
Remake atrocious
Lao Schifrim
Adam ClaytonSlide30
Character of song can remain despite large timbre changes
Christopher
Tyng