|
TRADITIONAL music for wind instruments gives each instrument
only one note at a time. More recently, players of wind instruments have
been playing, and contemporary composers calling for multiphonics: two or
more notes sounded simultaneously. We have studied these both in terms of
the sounds produced and the acoustical properties of the instrument in
the configuration ('fingering') which produces them.
Most musical instruments consist of a non-linear control oscillator (a jet of
air,
in the case of the flute) coupled to a linear harmonic resonator (the
column of air inside the instrument). A flute player blows across the top of a
hole open to the air, so the input is close to atmospheric pressure. Unlike
most other wind instruments, in which the player's mouth seals the input, the
flute
therefore operates at minima rather than maxima of acoustic impedance.
|
Until recently this has impeded studies of flute acoustics because large
dynamic range is required to resolve details of the impedance minima. A
technique developed in this laboratory has the required range and precision, and led
to a range of studies on the flute and other instruments.
In normal operation, mode locking occurs so that the vibration régime
is periodic. In multiphonics, two or more resonances, which are not harmonically
related, can be played simultaneously. The multiphonic corresponds to a
non-linear superposition of the two vibration régimes, in which harmonics
and heterodyne components are present at low values of the acoustic impedance.
Elizabeth
O'Connor, John
Smith,
John Tann & Joe Wolfe
|
