Matthias Demoucron

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Publications

• Introduction
• Sound examples

Control of the model

The model necessitates the dynamical control of at least two parameters in order to be driven: bow speed and bow force. Additionaly, the position of the bow on the string and the pitch could be controlled as well. In the following example, the model is played using a WACOM tablet. The velocity is computed from the motion of the pen in one direction. The bow pressure is related to the pressing force of the pen on the surface, and the position of bowing on the string, to the perpendicular direction.

Click on the picture to watch the movie

Influence of the parameters

An interest of physical modelling consists in making possible to play with the different parameters and in producing this way some sounds that would not be so easy to obtain in the "real" world.

For instance, the string is defined by a set of parameters including its length, tension, density, Young modulus, damping coefficients, or friction coefficients. The length and the tension are mainly used to set the pitch of the string, whereas other parameters can be used to get more "exotic" sounds. Here are some examples of such a play with parameters.

• The damping coefficients affects the decay time during the free vibration of the string.

  Normal damping	Low damping	High damping

• Young modulus is used to set the inharmonicity of the string.

  E=0 N/m2	E=20e9 N/m2	E=40e9 N/m2

Empirical patterns

Fast to and fro motion of the bow with a small accentuation on the first note: the velocity is alternatively positive and negative, whereas the force decreases.
Rather similar bow stroke with a quicker motion.
Rebounds of the bow on the string. Bow speed is almost constant and bow pressure shows successive spikes.

C4 sharp	A5 moll

Gesture models

• Sautille

  The rebound of the bow on the string is represented with half a sine, the bow velocity being assumed to be constant or to alternates between positive and negative values. Here are two sound synthesis.

  Rather long contact time between the bow and the string.	Short contact time imitating a rebound with the bow stick.

• Martele

  Bow velocity presents a bell like shape. Bow pressure is more complex to describe. It roughly presents a decreasing (example 1), but can also be more finely described in order to get "bad executed" bow stroke (example 2).

  Example 1	Example 2

• Tremolo

  In that case, the velocity is modelled with a sine representing regular to and fro motion of the bow. It is possible to get different kind of tremolo by playing on the following parameters: bow force (constant, here), bow speed frequency and amplitude.

  "Classical" tremolo	Harsh tremolo, almost crushed on the string	Very light one, with low bow pressure