The original theme was composed by Ron Grainer and realised by Delia Derbyshire of the BBC Radiophonic Workshop, with assistance from Dick Mills. The various parts were built up using musique concrète techniques, by creating tape loops of an individually struck piano string and individual test oscillators and filters. The Derbyshire arrangement served, with minor edits, as the theme tune up to the end of season 17 (1979–80). It is regarded as a significant and innovative piece of electronic music, recorded well before the availability of commercial synthesisers or multitrack mixers. Each note was individually created by cutting, splicing, speeding up and slowing down segments of analogue tape containing recordings of a single plucked string, white noise, and the simple harmonic waveforms of test-tone oscillators, intended for calibrating equipment and rooms, not creating music. New techniques were invented to allow mixing of the music, as this was before the era of multitrack tape machines. On hearing the finished result, Grainer asked, "Did I write that?"[citation needed]