Several of Paul's compositions have involved making extensive spectral analyses of various sounds. Working with several trombone 'lip' multiphonics, as performed by the trombonist John Kenny on alto and tenor-bass trombones, has generated a large resource of acoustic data (and compositional material). These analyses have been made using the computer programs Hypersignal and Audiosculpt which enable detailed analyses of spectra at precise time-points (small 'windowed' segments of the sound, typically between 1/20th - 1/40th of a second) as well as tracing the development of individual component partials throughout the multiphonic (with typical durations of around 15-20"). The Hypersignal spectrograph reproduced below is an example showing the Bb (233 Hz) trombone tone with its harmonics gradually moving into the multiphonic (the central part of the picture) and returning to the Bb at the end. The duration of the sound in this example is c.23". Amplitude is colour-coded in the spectrograph: white = loudest, yellow = 5dB less, orange 5dB less than yellow etc.
The graph below (right) shows the spectrum formed at one time-'slice' in this multiphonic. This graph comes from a spectral analysis of the same multiphonic as the spectrograph below (left), but with a much finer frequency resolution. The analysis was made by Dr R. Parks using his own program at the Dept. of Physics, Edinburgh University.
Spectral analyses of the following sounds have been made:
The results of these analyses have been integrated into recent compositions. However, a detailed account of the trombone multiphonic analyses (with all the 'raw' data) and the compositional techniques deriving from these analyses can be found in Edinburgh University library and The Reid Music library, Faculty of Music, Edinburgh University. [Document accompanying the folio of compositions submitted for Ph.D.].