ï~~1.3 Why Real Time?
The first author has made a number of pieces based on
PhM mostly non-realtime [29,10]. Though PhM in realtime
(RT) has been exploited for some time its complexity and
processing demands has prevented extensive usage. With
increasing processing power more advanced models can
run in RT and appropriate live control-systems be
investigated.
RT control is important when exploring the
"playability" of a model either in the studio or on stage. It
allows one to "sense" the interactions of the instrument
and immediately evaluate its output. The authors wished to
control individual keyholes of the virtual bass-clarinet in
close coordination with fingering sequences specified for
the live player. Each hole interact dynamically with the
tube via a hole-connection that can be gradually opened or
closed.
Realtime control of the model was used both in the
studio and on stage. It proved a very effective device in
searching a parameter-space. Modal synthesis tend to have
many interacting parameters, certain changes may cause
multiple effects, such as e.g. lowering number of modes
may increase overall amplitude, due to less modes that
interact. These can be quickly estimated through aural
feedback.
The parameter-space of modal synthesis is not
linear in the sense that linear interpolation of physical
parameters would create an even-spaced progression from
one timbre to another. Interpolating presets had to be
carefully considered. Interpolation presets does not
necessarily create an "interesting" transition between
otherwise fascinating states. RT feedback proved again the
quickest way of finding "zones of interest".
We wanted to put the models live capabilities to a
test, making full use of its many controls in RT. By
pushing the limits we wanted to address problems thus
provoked and device solutions, some of which will be
discussed under implementation in section 2.
1.4 Multiphonics - an extended timbre-study
Many has noted the "electronic" sound-quality of
multiphonics [1]. True, there is a bit of a ring-modulator
gone wild about them. But they are more than just
interesting new timbres. The way they physically work and
manifest themselves as "multiple sounds" goes beyond the
mere coloristic. For the first author multiphonics constitute
not only a wish for a large sound palette, but a quest for
composing at the principles of forked fingerings in an
integral way. A search for a link between a physical
mechanism and its manifestation in sound where multiple
components participate in the coordinated production of
more than one layer of sound.
Understanding the physical-acoustical conditions
necessary for the production of multiphonics in
woodwinds has been described by some authors [3].
Analysis of multiphonics naturally asks for a notational
reduction for it to be practical. Main criteria for listing
them found in methods is lowest (heard) pitch, usually
with some additional information about dynamic range,
speed of response, timbre, ease of playability, possible
alternations, etc.
Multiphonics are seldom those fixed entities they
appear in the methods [1,2]. They have emerging qualities
that largely determine the order of appearance and salience
of each component, many of which the player can control.
Clarinettists are fx. known to be able to produce different
multiphonics from the same fingering only by changing
aspects of the embouchure, reed-position and air-pressure.
This domain is rarely systematically described. The first
author consequently attempted a physical-acoustical
categorisation of the multiphonics based on 3 criteria:
1) perceptual, concerns how a multiphonic is perceived.
An empiric, but useful number of categories is proposed:
* homogene /heterogene
* pure /electronic
* fine / coarse
* fused /split
* stable /rolling
* harmonic / inharmonic
A main division is if the multiphonic provokes a single
fused percept or multiple simultaneous percepts.
2) physical, concern how a multiphonic is obtained (esp.
with regard to type of fingering). They where labeled:
* natural
* register-key (proper or fake)
* perforated
* trill-keys
* forked. resistant (altissimo-fingerings underblown)
Each type of fingering describe a specific relation between
air-column and nodes.
3) embouchure, concern how the multiphonic is excited.
This rather intricate category consists of:
* reed-position of lips at tip, mid or base of reed
allowing more or less of the reed to vibrate.
* lip-pressure on the reed and how much air
that slips through the sides of the mouth.
* air-pressure determines together with lip-pressure
the speed of air passing the reed / mouthpiece.
* reed-type either soft (elastic) helping the
production of multiphonics or hard (stiff) enforcing
fundamental and a strident timbre.
* oral cavity is known to play an important role,
but is relatively little described in the literature.
For fingerings whose output is ambiguous and difficult to
notate exactly an action type notation combined with
finger-tabulature was adopted. A graphical notation of the
players embouchure was invented and is described in the
score [11].
433
