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controller. The strength of shadowing lies in the fact that performer and Live Algo-
rithm express a strong coherence, with tightly unified temporal patterning. In its
simplest form, shadowing achieves strong but trivial participation, and little or no
leadership, autonomy or novelty. However, even in this simple form, the appear-
ance of coherence can have a strong effect for both performer and audience, and
can contribute to the sense of autonomy of the system, and the generation of nov-
elty through its interactive affordances. More complex forms of shadowing might
involve more sophisticated musical responses such as counterpoint and harmony.
A system based on rhythmic entrainment and temporal anticipation rather than an
instantaneous response could achieve shadowing in a way that exhibited creativity,
and the possibility to switch to a leadership role.
6.4.1.2 Mirroring
Mirroring involves some extraction of more abstract stylistic information or musi-
cal content from the performer, which is “reflected” back to the performer in novel
ways. Pachet's
Continuator
system provides a highly sophisticated example of mir-
roring (Pachet
2004
). System E in Fig.
6.1
would be the most apposite context.
In human performance mirroring is used as an explicit device or appears as a
more implicit principle of building on a shared mood or theme. As with shadowing,
the system predominantly takes the lead from the performer. This clearly demon-
strates participation, and can contribute to a form of collaborative creativity through
the opening up of new possibilities. As with shadowing, an appearance of autonomy
comes with the sense that the musical output is coherent. By successfully achieving
the local goal of mirroring with an unknown performer the system demonstrates a
basic autonomous capacity, perhaps even implying that it “understands”.
The mirroring approach is more immediately capable of leadership, but like shad-
owing must be enhanced by other behaviours to achieve this ends. Choices about
how the mirroring is managed can lead to greater autonomy. In order to achieve
leadership the mirroring must be capable of appropriate alteration to the style being
reflected. Shadowing and mirroring preferably require an interaction scheme where
the performer's output can be clearly distinguished from the environment, rather
than where the state of the environment, consisting of the mixed output of both per-
former and Live Algorithm, is given as input. Naturally this can be achieved if the
system is capable of distinguishing its own output from the mixed input, but this is
challenging in practice.
Mirroring fits the fully fledged Live Algorithm scheme of Fig.
6.1
H, where
f
involves the storage, analysis and retrieval of incoming feature data
p
.
6.4.1.3 Coupling
Coupling refers to a system's behaviour that is largely driven by its own internal gen-
erative routines, which are perturbed in various ways by information coming from
