Description of the System

The additive synthesis engine used for this project was implemented on a system consisting of an SGI workstation running IRCAM's FTS software. For the purpose of interpolation we constructed a 2 dimensional expressive timbral subspace covering a 2 octave clarinet range with three different dynamic levels. (See Figure 3).

Figure 3: Expressive Timbral Subspace

This additive parameter sub-space was built by analysing clarinet sounds from the Studio-on-Line project at IRCAM, recorded at high quality, 24 bits, 48 KHz and using six different microphone positions [Fin96]. Nine analysis files are obtained, three for each of three chosen pitches (pp, mf, and ff dynamics of F3, F4, and F5). Available synthesis parameters include global parameters such as loudness, brightness, and panning as well as the timbral space interpolation x- and y-axis values, and frequency shifting. An additional parameter - harmonic deviation - allows the scaling or removal of all frequency deviations from perfect harmonicity in the partials. The resulting output is an interpolation between the four additive model parameter files of each quadrant; first FTS performs two interpolations between the x-axis borders of each quadrant, and then a third interpolation between these two results is taken for the final output, according to the information received for pitch and dynamics from the controller/mapping. 1.

Although this approach seems very similar to the one taken in sample synthesizers - with the advantage of having a control (by interpolation) over the sustained portion of the sound - there is an important conceptual point to our approach which should be noted. By considering the additive method, we consider interpolation not between actual sounds but between models, and thus the issue of modeling is central to this work.

A simple noise source is also modeled in order to provide an approximation to the actual clarinet sound, since the models used for interpolation are issued from additive synthesis and therefore do not contain the noise components of the original sound. Within all mapping examples the noise level is controlled by a ratio of breath pressure to embouchure.

We should point out that our synthesis model considers "dynamics" to be strictly a timbral quality, based on the additive models for the normalized pp, mf, and ff clarinet sounds. Actual volume change is handled as an independent parameter.