Gijs Levelt started studying with Charles Green at the Sweelinck Conservatory in Amsterdam when he was sixteen. He graduated from the conservatory in 1997. He participated in classes from a number of guest tutors, including Bobby Shew, Jimmy Owens, Peter Masseurs, Jahnavi Jayaprakash, Marcus Stockhausen and Erik Vloeimans.

Since 1997 Gijs Levelt performs with and composes for De Amsterdam Klezmer Band. Besides the traditional klezmer repertoire the band plays band members' own compositions, which are increasingly influenced by Gypsy music from the Balkans with plenty of room for improvisation. The first, self-titled CD by De Amsterdam Klezmer Band was released in 1999, the second one, titled ‘Mala Loka’ in 2000. The third CD by this band, ‘Limonchiki’, was released in October 2001on the American label Knitting Factory. The band has toured in Turkey, Slovenia, Switzerland, Germany, England, Belgium, Italy and the USA. In 2000 De Amsterdam Klezmer Band was the house band for the television broadcasts of the NPS Culture Awards, the signature tune of which was composed by Gijs.
At the end of 2002 De Amsterdam Klezmer Band recorded a CD in Istanbul with the Galata Gypsy Band from Edirne, Turkey. At the start of 2003 the band conducted a tour of the Dutch club circuit in collaboration with actor/singer Bob Fosko.
Together wiith flautist Ned McGowan, Gijs Levelt forms the duo Messing met PVC, playing a fusion of Balkan music, jazz and contemporary compositional music. In November 2002 they toured in Bulgaria with guest singer/lafta player/percussionist Martha Mavroidi, who specialises in Bulgarian music. They also participated in a recording session for the Bulgarian National Radio with kaval virtuoso Theodosii Spassov.

Gijs Levelt has taken classes with Rafael Reina at the Conservatorium of Amsterdam since 1995. The classes explore the theory of Southern Indian (Karnatic) music and how it can be applied to contemporary compositional and improvisational music practice. Gijs took several master classes with the Southern Indian singer Jahnavi Jayaprakash as part of this program. In 1999 Gijs concluded this course and, together with flautist Ned McGowen, went on to found the concert series The Karnatic Lab, which is dedicated to this type of music and is staged in the cultural centre De Badcuyp. They also organise the annual Karnatic Lab Festival. January 2001 saw the first edition of Karnatic Lab On Tour, with a series of concerts in New York.
Gijs toured in India twice with the octet Bhedam (which includes flautist Ned McGowan, violin player Oene van Geel and bass player Mark Haanstra) , performing in collaboration with vocalists Jahnavi Jayaprakash and T.S. Seshagopalan, and percussionists B.C. Manjunath and Udayraj Karpuur. At the start of 2002 they recorded their debut album ‘Rickshaw Chase’ in Bangalore, India. In 2002 Bhedam toured the Dutch jazz circuit.
In July 2000 Gijs performed at a number of very well-received concerts in Spain by the ensemble for contemporary music, The Interval Chamber. After all this it was a natural step for Gijs to become co-founder of the Axyz Ensemble in 2003.

At the start of 2003 Gijs Levelt founded the quartet Deep Fried Angel Fish. The band, with Theo van Tol on accordion, Tobias Klein on alto saxophone and bass clarinet and Meinrad Kneer on double bass, plays accessible tunes with a sharp edge, improvised jazz influenced by klezmer, Latin and Balkan music.
In 2002 Gijs played with the trio Fig Tree 3, with guitarist Timuçin Sahin and double bass player François Chanut.
At the start of 1996 Gijs founded the Dutch Jazz Trio, with singer Fay Claassen and guitar player Vincent Koning. The trio toured Japan in the summer of the same year.
From 1995 Gijs led the jazz quartet Four Wheel Drive, together with saxophone player Wim Lammen. The band toured in Turkey and Slovenia and made recordings and conducted workshops at the High School for Music Ljubljana. In December 1998 the ConcertZender broadcast a special program dedicated to this quartet. In 1999 live-recordings were made for the ConcertZender.
Gijs played lead trompet in the Jazzmania Bigband conducted by Peter Guidi, which won several competitions, toured in France, Germany, Hungary, the Czech Republic and Spain, and released its first CD at the end of 1996.

Gijs performed in the Netherlands, Germany, Ile de la Réunion (Africa) and Switzerland with the funk band Traffic Jam. He worked as a substitute trumpet player for Fra Fra Sound, Fra Fra Big Band and various salsa, Hindustani and African bands. Gijs has performed regularly as a special guest with trip-hop/drum&bass group Mimezine. Gijs currently plays with Soulsurvivors, Food for Funk and The Herb Spectacles (a spin-off of The Treble Spankers).

Teaching practice
In addition to his private teacing practice, Gijs Levelt held a permanent teaching at the Amsterdam Music School from 1999 to 2002. He conducted jazz workshops at the MSA and the High School of Music in Ljubljana, Slovenia. Together with Ned McGowan he regularly conducts ‘Karnatic Lab workshops’.