Esa Onttonen (b. 1975) grabbed the guitar for the first time at the age of nine and got familiar with jazz music on his hometown's, Jyväskylä's music school's guitarlessons. When he graduated from the high school, he was accepted straight away to the jazz department of Sibelius Academy where he started his studies in 1994. Onttonen studied guitar for three years under Jarno Kukkonen and Raoul Björkenheim until he changed his major to jazzcomposition.

One of the earliest bands that performed Onttonen's compositions was organist Mikko Helevä's Big Brother Quintet. Later Onttonen has played and recorded as a sideman with Mirja Mäkelä Band, Jenny Robson Band and violinist Ari Poutiainen's NonAlike. The two own bands of the guitarist have been Gourmet, a band leaded with saxophonist Mikko Innanen, and Gnomus Trio that performed totally improvised music. In addition Onttonen organized together with Gnomus and Nuijamiehet-band a record label Fiasko Records, whose first release was Gnomus, an album recorded live at Agricola Church in January 2000. The reputation of Gnomus reached also the concert organizers and the exciting music of the band could be soon heard live on the clubs and festivals widely around Finland.

Onttonen's diploma work for Sibelius Academy was a series of compositions called "Approximately five songs for a big band and a saxophone" that UMO Jazz Orchestra premiered in November 2001, Mikko Innanen performing as the soloist. This 45-minute concert got good reviews and Onttonen was immediately raised to the group of the best jazzcomposers in Finland. Later on he has been doing compositions for the Big Band of Jyväskylä, UMO and smaller ensembles. In 2006 the guitarist composed a huge work for the City Orchestra of Mikkeli.

As an arranger Onttonen has done two works for UMO, organist Jukka Gustavson and saxophonist Jukka Perko performing as the soloists. Besides the big band arrangements, Onttonen has done co-operation with Avanti! and taught electric guitar, ensemble work and pop/jazz theory at the University of Applied Sciences of Oulu.