Jeroen Paul Thesseling (born 13 April 1971) is a Dutch fretless bass player, most famous for his work in the German progressive death metal band Obscura[1] and the Dutch progressive death metal band Pestilence.

The period following, Arabic microtonal and contemporary classical music inspired him to focus primarily on fretless bass.

[13][14][15] In late 2014, he founded the jazz fusion group Salazh Trio[16] featuring legendary Cuban drummer/percussionist Horacio Hernández.

[17][18][19] In October 2019, he founded the fusion-world-metal group Quadvium with fellow fretless bass player Steve Di Giorgio.

[20][21][22] From 2020 till 2022 Jeroen rejoined the German technical death metal band Obscura after a nine-year break.