The Prisma project

How do construction methods, material and play of a musical instrument influence its sound? Answers to this question of musical acoustics can give important insights to instrument makers and musicians. In many papers, researchers have tried to explain properties of instrumental sounds by using physical models. This approach was successful in many cases; however, subtleties like the timbre of a tone cannot be understood by physical models in general. Indeed, every physical model assumes simplifications about the instrument. As an example, consider a recorder model: in general, an exact cylindrical bore and perfectly smooth inner walls are assumed. On the other hand, it seems that the timbre of a tone is relevantly influenced by the irregularities of the instrument. Hence, physical models explain only a certain part of the musical reality.

In the Prisma project we pursue a different way. We consider the sound generation as a black box which generates a sound depending on the making of the instrument, the player, the surrounding space and other parameters. At the output side of the black box, measurable quantities (features) related to the played sound appear. Prisma is a system which computes and visualizes these features. By varying the input parameters in a systematic way and observing the resulting features at the output, a user can improve his understanding of his instrument.

Input   Black box   Output
Surrounding space
Musical context
Sound production in the instrument
Fundamental frequency
Sound energy
High partials to signal ratio (a measure of the overtone content)
Spectral centroid (a measure of the overtone or noise content)
The Prisma project began in 2001 as a collaboration between the Berne University of Applied Sciences (Engineering an Information Technology) and the Zürich University of the Arts (Department of Music). It was supported by the Swiss National Foundation (DORE program) between 2003 and 2005.

An important milestone was the launch of the Prisma-Realtime system in 2005. Since then, the software has been improved and supplemented steadily. Whereas former versions of Prisma-Realtime mainly served as a tool for visualizing the basic spectral data (frequencies, magnitudes) of a tone in real time, the present Version 1.3b (March 2010) enables users to inspect the time behaviour of features derived from these spectral data. In addition, the analysis of transient phenomena (e.g. articulation of instrumental tones) and of low tones (ca. 85 Hz and higher) are possible.

As a result of a research project, Prisma-Realtime can be downloaded freely from this website -> Publikationen, Downloads.

The -> Gallery contains examples of Prisma tone analyses.