It was mathematician Joseph Fourier, whilst experimenting on heat transfer work, who first proposed that any periodic signal could be reconstructed from a series of pure sinewaves of different frequencies and this little experiment does confirm his idea. However, although the timbre of the ringing in the synthesis is pretty much identical to that of the recording of the real lampshade, the synthesis is pretty ‘flat’ sounding as there is no amplitude variation and decay envelope. As time passes the ringing is changing as vibrational energy sloshes around in the metal shade and gradually dissipating. The higher partials decay at a more rapid rate than the fundamental and the relative levels of partials are constantly varying in repsect to each other – its a complex sound that shimmers and ripples with a life of its own. The synthesis is merely a snapshot of a frozen moment in time – it’s no wonder it sounds so one dimensional in comparison to the real sound. It takes a great deal of work to sculpt the bland tones of synthesised pure sine, sawtooth and square waves into something that is musically interesting enough to be useful in a composition. Derbyshire would add effects such as tube amplifier and tape saturation distortion, tape wow (vibrato), phasing, filtering, reverb and delay to breathe life into her sounds.
The lampshade used in these recordings is a ‘Coolicon’ utility lighting shade, British Patent No 419602, Registered Design No 777912. The actual lampshade that Delia used at the Radiophonic Workshop to make the sounds for ‘Blue Veils and Golden Sands’ is currently on display at the Science Museum in London.