John William Stevens (1940 - 1994) was an English drummer and a founding member of the Spontaneous Music Ensemble. Stevens played alongside a large number of prominent free improvisors in the SME, including Derek Bailey, Peter Kowald, Julie Tippetts and Robert Calvert, but from the mid-1970s, the make-up of the SME began to settle down to a regular group of Stevens, Nigel Coombes on violin, and Roger Smith on guitar. From 1983 Stevens was involved with Community Music, an organisation through which he took his form of music making to youth clubs, mental health institutions and other unusual places. Notes taken during these sessions were later turned into a book for the Open University called Search and Reflect (1985). SME played for its last time in 1994, when it included John Butcher. Stevens died later that year. Emanem boss Martin Davidson has written an appreciation of Stevens, which you can read here.