Structure is fundamental to almost every kind of music, even those genres that emphasise improvisation, such as most jazz. Free improvisation, however, eschews the trappings of structure and even composition, allowing musicians unrestrained autonomy to create the rules of a piece of music as they perform it. Born in musicians’ circles in the late 1950s and ’60s, this avant-garde jazz genre still finds a small yet dedicated audience among aficionados with a taste for the atonal. This short film features a performance from some of the giants of free jazz at Cafe Oto in east London. Amid the music, the performers, including the saxophonist Evan Parker, the percussionist Eddie Prévost and the bassist John Edwards, detail the philosophy of the form, including how its radical lack of rules gives rise to unique challenges – as well as transcendent moments – for both musicians and listeners.