Musical Virtuosity and Creativity - Computers and Creativity - page 120

Fig. 5.4 Example of a side-slip, given by (Coker 1997 , p. 50). Note how the first side-slip smoothly
continues in the 'right key' (here, D minor)
in which there are no more rules whatsoever. Playing out, in bebop, is a precisely
defined musical device whose mastery necessitates perfect control of the instrument.
The ability to play out 'the right way' can be considered a sign of a complete mas-
tery of the art.
The main way to play out is called side-slipping (or side-stepping ). Shim ( 2007 )
dates the origin of side-slipping back to Art Tatum, an acknowledged piano virtuoso,
who 'displayed his mastery of chromatic harmony by effortlessly floating in and
out of keys' (p. 183). A stepping stone of this evolution is probably the incursion
of modal improvisation in the jazz repertoire; with the famous tune 'So What' by
Miles Davis, based on a long repetition of a D minor chord. To avoid a 'tide of
boredom' due to this harmonic monotony, various techniques for escaping tonality
were invented, including side-slipping (Coker 1984 ,p.49).
Pedagogical definitions of side-slipping may be found in jazz theory topics
(Coker 1984 ; 1997 ,Levine 1995 ), with some variations. Side-slipping is a device
that produces a short sensation of surprise, in a context deemed too predictable
(Levine 1995 ). The idea is to play out-of-key, with the goal of momentarily creat-
ing tension, and then come back to the right key, which can be different from the
starting key. Most often, the out-of-key segment uses symmetry. For instance, it can
be the same phrase transposed a semi-tone higher. The listening impression is de-
scribed by Coker ( 1984 ) is as follows: 'Like the stretching of a rubber band, the
attuned listener seems to know that the player's excursion into another key is very
temporary and that he will snap back to the original key when the tension period is
over. In the meantime, the listener has been taken on a brief trip that has broken the
monotony of modality'. Side-slipping was intensively used by pianists like Lennie
Tristano (Shim 2007 , p. 183), and many others (John Coltrane, Allan Holdsworth)
and is now a classical ingredient of modern improvisation.
Figure 5.4 shows a typical side-slip, given by Coker ( 1997 , p. 50). The mechani-
cal dimension of the side-slip appears clearly: here a simple transposition of a 4-note
pattern one semitone up, and then down. Figure 5.6 shows a more complex example
of a side-slip produced backward in time, i.e. played before the non-transposed ver-
sion, creating an even more surprising effect (shocking, then deliciously soothing).
Note that such an effect would not work if played at low speed, as the time during
which wrong notes are played would be too long, creating a risk for the listener to
lose the sensation of tonality. As such side-slipping is not an ornamental device, but
a central feature of linear improvisation.
There are many variants of side-slipping, notably concerning the device used to
produce the phrase out of key , its length, metric structure, etc. (Coker 1997 ). For