Jeroen Paul Thesseling (1971) followed his first classical violin lessons at the age of 7 and started his study bass guitar in 1988 at the ArtEZ School of
Music in Enschede, the Netherlands. After playing metal and jazz in his late teenage years he collaborated with the Dutch group PESTILENCE from
1992 till 1994, recording their jazz-fusion influenced album 'SPHERES' (1993). Since 1995 he experimented with microtonal octave divisions, which
resulted in 'HAFNIUM' - study in 72-tone equal temperament (1999) and 'ARGON' - study in 18-tone equal temperament (2000). In 2005 Jeroen
recorded his first fretless work with the studio project ENSEMBLE SALAZHAR. Since that same year he plays exclusively fretless bass. From 2007
till 2011 he collaborated with the German group OBSCURA with whom he recorded the albums 'COSMOGENESIS' (2009) and 'OMNIVIUM' (2011).
During the period 2009-2012 he rejoined PESTILENCE after a 15-year break, recording the album 'DOCTRINE' (2011). Since 2011 Jeroen plays 7-string
fretless basses strung with a subcontra F#-tuning built by German bass luthier Warwick. In 2014 he founded the jazz-fusion group SALAZH TRIO with
whom he recorded their debut 'CIRCULATIONS' (2017).