Difference between revisions of "Taps paper"

From CSWiki
Jump to: navigation, search
(36 intermediate revisions by 3 users not shown)
Line 1: Line 1:
'''The Really Good TitleWithout TAPESTREA'''
Pasta Tree, E. Rat Pestay, Ape Treats
Department of Computer Science (yalso Music), Princeton University
Traditional software synthesis systems, such as Music V, utilize
an instance model of computation in which each note
instantiates a new copy of an instrument. An alternative is
the resource model, exempli�ed by MIDI îmono mode,î in
which multiple updates can modify a sound continuously, and
where multiple notes share a single instrument. We have
developed a uni�ed, general model for describing combinations
of instances and resources. Our model is a hierarchy in
which resource-instances at one level generate output, which
is combined to form updates to the next level. The model can
express complex system con�gurations in a natural way.
= Introduction =
In the 1940s and 50s, Pierre Schaeffer developed musique
concrete. Unlike traditional music, musique concrete starts
with existing or concrete recorded sounds, which are organized
into abstract musical structures. The existing recordings
often include natural and industrial sounds that are not
conventionally musical, but can be manipulated to make music,
either by editing magnetic tape or now more commonly
through digital sampling. Typical manipulations include cutting,
copying, reversing, looping and changing the speed of
recorded segments.
Today, several other forms of electronic/electroacoustic
music also involve manipulating a set of recorded sounds.
Acousmatic music [cite Dhomont], for instance, evolved from
musique concrete and refers to compositions designed for environments
that emphasize the sound itself rather than the
performance-oriented aspects of the piece.
The acoustic ecology [cite Schafer] movement gave rise to
soundscape composition [cite Truax] or the creation of realistic
soundscapes from recorded environmental sounds. One
of the key features of soundscape composition, according to
Truax, is that ìmost pieces can be placed on a continuum between
what might be called `found sound' and `abstracted'
approaches.î However, while ìcontemporary signal processing
techniques can easily render such sounds unrecognizable
and completely abstract,î a soundscape composition piece remains
recognizable even at the abstract end of the continuum.
Sound designers for movies, theater and art often have
a related goal of starting with real world sounds and creating
emotionally evocative sound scenes, which are still real,
yet transformed and transformative. Classic examples include
mixing a transformed lion's roar with other sounds to accompany
the wave sounds in ìPerfect Storm.î These sound designers
are ìsound sculptorsî as well, but transform sounds
to enhance or create a sense of reality, rather than for musical
Artists from all of the above backgrounds share the process
of manipulating recordings, but aim to achieve different
effects. We present a single framework for starting with
recordings and producing sounds that can lie anywhere on a
`found' to `unrecognizable' continuum. `Found' sounds can
be modi�ed in subtle ways or extended inde�nitely, while
moving towards the `unrecognizable' end of the spectrum unleashes
a range of manipulations beyond time-domain techniques.
In fact, the same set of techniques apply throughout
the continuum, differing only in how they are used. We call
this framework TAPESTREA: Techniques and Paradigms for
Expressive Synthesis, Transformation and Rendering of Environmental
TAPESTREA manipulates recorded sounds in two phases.
In the analysis phase, the sound is separated into reusable
components that map to individual foreground events or background.
In the synthesis phase, these components are parametrically
transformed, combined and re-synthesized using
time- and frequency-domain techniques that can be controlled
on multiple levels. While we highlight the synthesis methods
in this paper, the analysis phase is also integral as it makes
the synthesis possible.
= Related Work =
Related techniques used for musical composition include
spectral modeling synthesis [cite Serra/Smith] and granular
synthesis [cite ??]. Spectral modeling synthesis separates a
sound into sinusoids and noise, and was originally used formodeling instrument sounds. Granular synthesis, in contrast,
functions in the time-domain and involves continuously controlling
very brief sonic events or sound grains. TAPESTREA
employs aspects of both, using separation techniques on environmental
sounds and controlling the temporal placement
of resulting events.
Another technique used in TAPESTREA is an extension
of a wavelet tree learning algorithm [cite Dubnov] for sound
texture synthesis. This method performs a wavelet decomposition
on a sound clip and uses machine learning on the
wavelet coef�cients to generate similar non-repeating sound
texture. The algorithm works well for sounds that are mostly
stochastic, but can break up extended pitched portions. It can
also be slow in its original form. TAPESTREA takes advantage
of this technique by using a faster version of it on the
types of sound for which it works well.
3 Analysis Phase
TAPESTREA starts by separating a recording into deterministic
events or the sinusoidal or pitched components of the
sound, transient events or brief noisy bursts of energy, and the
remaining stochastic background or din. This separation can
be parametrically controlled and takes place in the analysis
Deterministic events are foreground events extracted by
sinusoidal modeling based on the spectral modeling framework.
Overlapping frames of the sound are transformed into
the frequency domain using the FFT. For each spectral frame,
the n highest peaks above a speci�ed magnitude threshold
are recorded, where n can range from 1 to 50. These peaks
can also be loaded from a preprocessed �le. The highest
peaks from every frame are then matched across frames by
frequency, subject to a controllable ìfrequency sensitivityî
threshold, to form sinusoidal tracks. Tracks can be ìmuteî
or below the magnitude threshold for a speci�ed maximum
number of frames, or can be discarded if they fail to satisfy
a minimum track length requirement. Undiscarded tracks
are optionally grouped [cite Ellis, Melih and Gonzalez?] by
harmonicity, common amplitude and frequency modulation,
and common onset/offset, to form deterministic events, which
are essentially collections of related sinusoidal tracks. If the
grouping option is not selected, each track is interpreted as a
separate deterministic event.
Transient events or brief noisy foreground events are usually
detected in the time-domain by observing changes in signal
energy over time [cite Verma and Meng, Bello et al.?].
TAPESTREA analyzes the recorded sound using a non-linear
one-pole envelope follower �lter with a sharp attack and slow
decay and �nds points where the derivative of the envelope is
above a threshold. These points mark sudden increases in energy
and are interpreted as transient onsets. A transient event
is considered to last for up to half a second from its onset; its
exact length can be controlled within that range.
The stochastic background represents parts of the recording
that constitute background noise, and is obtained by removing
the detected deterministic and transient events from
the original sound. Deterministic events are removed by eliminating
the peaks of each sinusoidal track from the corresponding
spectral frames. To eliminate a peak, the magnitudes
of the bins beneath the peak are smoothed down, while
the phase in these bins is randomized. Transient events, in
turn, are removed in the time-domain by applying wavelet
tree learning [cite Dubnov] to generate a sound clip that resembles
nearby transient-free segments of the original recording.
This synthesized ìcleanî background replaces the samples
containing the transient event to be removed.
Separating a sound into components in this way has several
advantages. The distinction between foreground and background
components is semantically clear to humans, who can
therefore work within the framework with a concrete understanding
of what each component represents. The different
types of components are also stored and processed differently
according to their de�ning characteristics, thus allowing
�lfexible transformations on individual components. Each
transformed component can be saved as a template and later
reloaded, reused, copied, further transformed, or otherwise
treated as a single object. In addition, the act of separating a
sound into smaller sounds makes it possible to ìcomposeî a
variety of pieces by combining these constituents in diverse
Describe analysis user interface?
4 Synthesis Phase
Templates are synthesized individually with transformations.
Gain / pan control exists.
4.1 Deterministic Events
Sinusoidal resynthesis.
Pitch and time transformations, real-time.
4.2 Transient Events
Phase vocoder is not stable but exists.
4.3 Stochastic Background
Wavelet tree learning.
Improvements can go here.
4.4 Event Loops
For repeating a single event.
Random frequency and time transformations on each instance.
Periodicity of event distributionñGaussian.
Can also be replaced by other distributions such as Poisson or
your own invention.
Density of eventsñhow frequently they recurñrelates to granular
synthesis for transients.
4.5 Timelines
Explicitly state when a template is played in relation to
other templates.
Timelines within timelines... multiresolution synthesis?
4.6 Mixed Bags
Controlling relative density of multiple templates...
Combines features of timelines and loops.
4.7 Score Language
Precise control beyond what sliders can provide.
Any other speci�c features?
4.8 Pitch and Time Quantizations
Quantize pitch to a scale.
A few pre-programmed pitch tables or one that's user programmable.
The ability to change pitch table on a timeline would be good
Quantizing time to a time grid for rhythm.
These could probably be done through chuck, but maybe there's
a clean way to do it through tapestrea itself.
There is also a secret (not-so-secret) reverb face. Include?
5 Discussions/Contributions/Sound samples/
6 Conclusion
Real references to be added.
Dannenberg, R. B. (1989). The Canon score language. Computer
Music Journal 13(1), 47ñ56.
Dannenberg, R. B., C. L. Fraley, and P. Velikonja (1991). Fugue:
A functional language for sound synthesis. Computer 24(7),
Dannenberg, R. B. and C. W. Mercer (1992). Real-time software
synthesis on superscalar architectures. In Proceedings of the
International Computer Music Conference, pp. 174ñ177. International
Computer Music Association.
Lindemann, E., F. Dechelle, B. Smith, and M. Starkier (1991).
The architecture of the IRCAM musical workstation. Computer
Music Journal 15(3), 41ñ49.
Mathews, M. V. (1969). The Technology of Computer Music.
Cambridge, Massachusetts: MIT Press.

Latest revision as of 16:10, 12 March 2006