In the draft constitution published in the Musical Times of June 1969, Cardew defines a scratch orchestra as: "a large number of enthusiasts pooling their resources (not primarily material resources) and assembling for action (music-making, performance, edification)". The Orchestra reflected Cardew's musical philosophy at that time. This meant that anyone could join, graphic scores were used (rather than traditional sheet music), and there was an emphasis on improvisation. The Scratch Orchestra arose from Cardew's 'Experimental Music' class at Morley College, London, which served as a venue for extra rehearsals for Scratch Orchestra concerts, but Scratch Orchestra rehearsals were also held separately. New Zealand artist/musician Philip Dadson was amongst those at Morley College who were in the foundation group for the Scratch Orchestra and, after returning to New Zealand, established a NZ Scratch Orchestra in 1970, which evolved into the group From Scratch in 1974.
The first meeting of the Scratch Orchestra was at St Katharine Docks , 1 July 1969. It was announced by means of a "Draft Constitution", published in The Musical Times in June 1969. The Draft Constitution set out categories of musical activity: Improvisation Rites, Popular Classics, Compositions, and Research Projects. Cardew also proposed that the responsibility of programming of concerts be assigned in reverse seniority, so that the first concert, on 1 November 1969 at Hampstead Town Hall, was designed by Christopher Hobbs, an eighteen-year-old student of Cardew's at the Royal Academy of Music.
Despite the emphasis on free improvisation, the varying experience of the members, and the "do your own thing" free aesthetic of the time, the Scratch Orchestra was a disciplined ensemble. Eventually the strains of Cardew's "reverse seniority", tensions between musically-trained and non-musically-trained members, and an increasing interest in political aesthetics led to a gradual change in the activities, and then the outlook of the ensemble. It was effectively inoperative by 1974.