As jazz marks the 100th anniversary of John Coltrane's birth this month, previously unheard recordings known as the Tiberi Tapes are shedding new light on how the saxophonist abandoned commercial success to pursue free jazz. The tapes capture Coltrane's nightclub residencies between 1960 and 1964, revealing the experimental process behind his shift from the accessible, radio-friendly sound of hits like My Favourite Things to the confrontational, structure-defying improvisation that alienated many listeners and critics by 1965.

The recordings were made secretly by fellow saxophonist Frank Tiberi, who hid a Magnavox TR-100 tape machine's microphone in his overcoat sleeve during Coltrane's extended club residencies at venues including Manhattan's Jazz Gallery and Philadelphia's Pep's Lounge, changing reels every 30 minutes to capture as much material as possible. Over the four years, Tiberi amassed 80 reels and more than 60 hours of music, which he later shared privately with students and peers, including saxophonist Joe Lovano; Coltrane's pianist McCoy Tyner reportedly confirmed the band knew of and permitted the recordings for educational purposes. Coltrane died of liver cancer in 1967, aged 40, just two years after his radical performance at the 1965 DownBeat festival prompted walk-outs and scathing reviews.