Qawwali is Sufi Muslim devotional song built around a lead vocalist plus a chorus of six to ten men, backed by harmonium and tabla, with the group clapping the beat. Songs run 10 to 40 minutes and build in tempo and intensity toward an ecstatic state Sufis call 'hal'. Lyrics blend Urdu, Punjabi and Persian, and deliberately blur the boundary between human romantic love and love of God — the 'beloved' and 'wine' of the poems are theological metaphors as much as literal images. Knowing that double reading changes what the music sounds like.

The tradition is credited to the 13th-century Delhi Sufi poet Amir Khusrau (1253-1325), who served the Chishti order's spiritual master Nizamuddin Auliya. Nizamuddin's Delhi shrine remains the central historical site, with weekly Thursday-night qawwali still being performed there. Bulleh Shah (1680-1757), the Punjabi Sufi poet, provides the largest share of Punjabi-language lyrics ('Bulleya Ki Jaana', 'Chal Bulleya'). In 1948 Nusrat Fateh Ali Khan (NFAK, 1948-1997) was born in Faisalabad into a hereditary qawwali family; he inherited his father's group in 1971 after his uncle Mubarak Ali Khan's death. Karachi's Sabri Brothers (Ghulam Farid 1930-94, Maqbool 1945-2011) held the Chishti-traditional ground with 'Bhar Do Jholi Meri' (1975) and 'Tajdar-e-Haram' (1980). NFAK's 1985 WOMAD appearance introduced him to Peter Gabriel, whose Real World Records released his 'Mustt Mustt' (1990) — remixed by Massive Attack, it opened the qawwali-into-trip-hop channel. He died of liver failure in London on 16 August 1997, aged 48. His nephew Rahat Fateh Ali Khan (1974-) inherited the group and pushed qawwali into Bollywood soundtracks (Kabhi Alvida Naa Kehna 2006, Om Shanti Om 2007).

The first three to five minutes are typically a quiet harmonium introduction and lead vocalist's exploration ('alap') where the beat has not yet arrived. When the tabla enters and the clapping starts, watch for NFAK's 'sargam' — passages in which he sings the solfège syllables 'sa re ga ma pa dha ni sa' as pure melodic improvisation. That sargam-into-repetition arc is his signature. Sabri Brothers' 'Tajdar-e-Haram' (1980) shows the traditional 40-minute form; Atif Aslam's 2015 Coke Studio 7-minute reworking of the same lyric is a useful contrast.

For a short entry, NFAK 'Mustt Mustt' (1990). For the full form, NFAK 'Allah Hoo Allah Hoo' in an unedited 40-minute recording. For traditional Chishti-style qawwali, Sabri Brothers 'Tajdar-e-Haram' (1980) and 'Bhar Do Jholi Meri' (1975).

The word 'qawwali' comes from the Arabic 'qaul' (utterance), originally meaning the recitation of the Prophet Muhammad's sayings before it was applied to Sufi poetry. NFAK's passport listed his profession as 'qawwal', not singer. Peter Gabriel has described NFAK's 1985 WOMAD performance as the single most intense musical experience of his life. Amjad Sabri, the Sabri Brothers' successor, was assassinated in Karachi in June 2016 in a sectarian attack at age 46.