The Spontaneous Music Ensemble (SME) was a loose collection of free improvising musicians convened beginning in the mid-1960s by the late South London-based jazz drummer/trumpeter John Stevens and alto and soprano saxophonist Trevor Watts. SME performances could range from Stevens-Watts duos to gatherings of more than a dozen players. One can loosely divide the group's history into two periods: the more horn-oriented earlier ensembles (typically with some combination of Watts