Spectral is played entirely on the solo viola, the bass range of which has been extended by tuning the C-string down to G and then by transposing its sounds down further by digital means. Spectral takes as its starting point the song of the hump-backed whale, of which the opening ARIA is an exact transcription.
The subsequent sections are developments of its individual elements. The tape echoes were suggested by the whale's submarine acoustic environment, in which its melancholy tones rebound alternately off the sea-bed and the surface as they die away. The title 'Spectral' relates not only to the sound/colour spectrum used in the music, but also to the ghostly character of the song in which the whale seems to be singing of its own passing.
First performed by the composer assisted by the other three members of the live-electronic group Intermodulation at a MacNaghten concert in 1972 at St John's Smith Square.
The sounds of the live viola are picked up by a contact microphone and fed into a delay system and modified and multiplied. The exact nature of the electronics may be varied according to what is available. A minimum of two players is needed, one on viola and one for electronics. The coloured lighting is an important part of the piece and a lighting engineer will be required to follow the detailed lighting plan provided with the score.
The original technical explanation and guidelines are included in the score, which was originally written for performance with the VCS3 (synthesiser). Additional more recent documentation is also available from Composers Edition to help with both technical and interpretative aspects of a performance.
'Perhaps the most coherent and satisfying work of this concert was Tim Souster's Spectral ... Inspired by a now famous recording of the call of the hump-back whale, Souster avoided being merely illustrative and displayed considerable virtuosity both in the techniques of sound transformation and in developing new modes of expression for the viola itself.'
- The Times 31.3.74
'... clean and beautiful amplified viola line. The texture is thickened in layers, the colours intensified and the result is a piece capable of fulfilling any definition of music, traditional or otherwise.'
- Birmingham Post 2.2.76
'It was remarkable that the use of technical apparatus ... resulted in a truly romantic surrender to images of nature as in Spectral.'
- Rheinisher Merkur 11.5.73
This score comes with recorded extracts of live hump-back whale song as a guidance to performance.