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live laptop performers (e.g.
live coders
) who manipulate or even create small algo-
rithmic units—
f
's—in real-time.
Figures
6.1
E and
6.1
F show a direct parameter mapping between analysed source
and synthesiser control. If the functions
P
and
Q
are mutual inverses, a mapping
between them is trivial,
Q
=
P
−
1
, and the system is a (possibly distorted) musical
mirror. Alternatively, the relationship between
P
and
Q
and the mapping between
them may be so complex that a participating musician is challenged to find any
obvious correlation. These systems can only be a vague prototype of a Live Algo-
rithm as they are only automatic, in the sense defined earlier; the initial conditions
that establish the mapping remain unaffected by context and new data. If there is
direct intervention by a user, as in
6.1
E, the system as certainly not autonomous.
These systems cannot achieve autonomy because they are overwhelmingly reactive
(for example it may not play in the absence of sound or pause in the presence of
sound). Any attempt to move beyond this basic feedthrough device requires algo-
rithms that do more than provide a huge switchboard of parameter connections, i.e.
an
f
module (see below).
Systems E and F may be used in certain
sound installation
contexts, including
situations where
Ψ
represents sonic and non-sonic environments (including move-
ment, brightness, etc.). Although the system is primarily a parameter map, a musi-
cian could monitor synthesis data that may inform his/her choice of synthesis pa-
rameter settings. This scenario is the accepted practice in live computer music, and
accounts for the vast majority of music produced in a live setting with computers.
Typically a software development system such as Max/MSP is used to implement
P
and
Q
functionality (although they are infrequently broken down into actual soft-
ware modules), with a visual display in the form of a “patch” and soft controls
such as sliders and dials to allow real-time (non-sonic) interaction with the system.
E might be considered as an enhanced instrument.
Systems
6.1
G and
6.1
H are syntheses of the basic A-F types. The most sig-
nificant elements are that they incorporate both analysing and performing within
the sonic domain, and establish a loop across the sonic and computational domains
by incorporating a functional module
f
. The ideal Live Algorithm operates au-
tonomously (system H); in practice, and until a true Live Algorithm is realised,
some degree of intervention is desirable (system G). Further exploration of these
challenges is presented in the sections below. Before this, we need to consider the
fact that all these processes occur in real-time, and also musical time, in which sonic
events have a past, present and future.
6.3.4 The Live Algorithm from the Outside
The Live Algorithm is, from the point of view of fellow performers, a black box. We
consider the functionality of the system as a whole in terms of the most primitive
description, the flow of data into and out from the device. Such a study points at
possible performance measures that can be utilised in Live Algorithm design.
