Kari "Sonny" Heinilä (b. 1966) started his music career with piano lessons in the Music School of Rauma. Later he changer his instrument to flute in the Music School of Pori and when he turned 12, the flute changed into saxophone. In 1984 Heinilä was accepted to the jazz department of Sibelius Academy where he studied till 1988. At the same time he studied composing privatly under Eero Hämeenniemi.

Heinilä arrived properly to the field of Finnish jazz in the mid-1980s through big bands. From Pori Big Band he moved to the Helsinki metropolitan area, first to Espoo Big Band and in 1987 to UMO Jazz Orchestra, where Heinilä played for seven years. More freer expression he got to practise in Edward Vesala's Sound & Fury where he played for some time, for example on the first ECM-release Lumi (1987). In 1995 Heinilä left UMO and began his work as a teacher on the jazz department of Sibelius Academy but the co-operation with UMO has still continued. Heinilä visited the orchestra as a conductor often in the beginning of 21st century and composed several works for the orchestra. In 2010 Heinilä returned to UMO to share the position as the artistic leader with Kirmo Lintinen.

In the late-1980s Heinilä played in several small groups, for example in the No Hope quintet of Severi Pyysalo, in the ensembles of pianists Seppo Kantonen and Jarmo Savolainen and in the 1990s in Jukka Linkola Tentet. The quartet album Blue Dreams of Jarmo Savolainen is besides Lumi the earliest ensemble recordings where Heinilä played. Although Sonny Heinilä wasn't that well-known as a bandleader in the middle of 1990s, his merits were noticed: in 1995 BAT Finland awarded Heinilä with a grant of 30 000 Finnish marks and he was chosen as the Pori Jazz Artist of the Year. The next year Heinilä's own trio was heard for the first time, including Swedish bass player Anders Jormin and drummer Markku Ounaskari.

In the beginning of the 21st century Heinilä recorded with i.a. keyboardist-composer Kari Ikonen's Karikko-band, Mia Simanainen's Ahava-group and on drummer André Sumelius' album Kaira that received the Emma Award as the Jazz Album of the Year. In 2003 both the soloalbum Antiqua (Celene) and the album of the Heinilä's quartet Lill' Lisa (Abovoice) were released. The latter album, including Heinilä's compositions and a couple Nordic folk songs, was a balanced record and a valuable document from the last years of the drummer Edward Vesala. In the beginning of the 21st century, in 2001, Heinilä was also awarded with the Georgie, Yrjö, Award.

Recently Sonny Heinilä has moved even closer to jazzy folk and chamber music. On the album Mosaique (Celene 2005) music is loaded with oriental moods and Heinilä uses for example the improvisation techniques of Turkish classical music. The Albero Quartet formed in 2004 moves in turn on the boarder of jazz and modern Western folk music. Although Sonny Heinilä's own musical exploration has been directed towards more and more exotic areas, he still performs with very jazzy groups. Besides the work as the artistic director of UMO, the saxophonist performas as a sideman once in a while with i.a. Samuli Mikkonen's 7 henkeä and 3 henkeä -projects and drummer Mikko Hassinen's Muuntaja Quartet. Heinilä left the post as the teacher of Sibelius Academy in 2002 but has been working as a teacher after that, for example in the teaching projects of regions' big bands.