began playing the drums at age 9. By 14 years old, he was a professional drummer and studio musician, and at 19 he entered the Rhythmic Music Conservatory. After two years of being taught by jazz drummers Ed Thigpen and Alex Riel, he put drums aside in favor of the piano, an instrument he had never been taught, and applied again at the conservatory – now as a pianist greatly influenced by Jørgen Nielsen and, later, Butch Lacy.
In the early 1990s Dahl began to play with Embla and Niels Præstholm, Thomas Agergaard, Anders Hentze, and Staffan Svensson. Their only CD, Embla showed Dahl's improvising, something that he would put aside for some years to explore the bebop tradition. During this collaboration, Dahl started to develop his own style, and met (via saxophonist Agergaard) drummer Thomas Blachman and bassist Lennart Ginman. Dahl appeared in Blachman jazz and hip hop projects during the 1990s, as well as records from the trio he formed with Ginman and drummer Frands Rifbjerg. This trio recorded the albums Will you make my soup hot and silver and Message from Bud. They went on to record a series of albums for the Japanese label Marshmallow Records – Blue Train and Be Boppish Rubbish Rabbit. They also recorded A Child Is Born, a quartet album with Bob Rockwell. Dahl also reunited with Thigpen and his trio, including Joe Lovano. They made three recordings together. Dahl appears on more than 150 albums
For the mid-1990s and well into the 2000s Dahl played with Anders Bergcrantz, Arild Andersen, Bent Jædig, Billy Harper, Cæcilie Norby, Charlie Mariano, Danish Radio Symphony Orchestra, Dave Liebman, Didier Lockwood, Ed Neumeister, Eddie Gomez, Eliot Zigmund, Ensemble Midtvest, Finn Ziegler, Gregory Hutchinson, Hanne Boel, Helen Davies, Jan Lundgren, Jerry Bergonzi, Jesper Lundgaard, Jesper Thilo, Jim Snidero, Johnny Griffin, Jon Christensen, Klaus Rifbjerg, Lars Danielsson, Lars Moller, Mads Vinding, Michala Petri, NHØP, Palle Mikkelborg, Per Goldschmidt, Phil Wilson, Philip Catherine, Putte Wickman, Reuben Rogers, Richard Boone, Suzanne Brøgger, Ted Curson, Thomas Hass, Tom Kirkpatrick, Tomas Franck, Ulf Wakenius, WDR Big Band, and Wynton Marsalis.
Dahl associated with the classical Ensemble Midvest as an artistic consultant, getting the ensemble to work with free improvisation. Among the many projects they worked on together was music for Fritz Lang's silent film Metropolis and Charlie Chaplin's City Lights and Don Q / Son of Zorro by Douglas Fairbanks.
Dahl has worked for several years with Bach's Goldberg Variations, arranged and played for prepared piano, alongside the Well-Tempered Clavier and Dahl's own 26 Chromatic Inventions – dedicated to Glenn Gould. In spring 2013 Carsten premiered his work The Fifth Dimension for symphony orchestra (dedicated to Per Nørgaard), with the DR vocal ensemble and the Copenhagen Boys Choir.
In October 2013 Dahl premiered his first piano concerto, played by the Odense Symphony Orchestra with Marianna Shiviyuan as the soloist. From 1992, he taught as a tenured associate professor at the Esbjerg conservatory. In 2011 he was appointed to a 5-year term as a professor in rhythmic contemporary music at the Rhythmic Music Conservatory in Copenhagen. He also works as an ambassador for Mental Health Fund, based on his own experiences, and regularly gives talks about anxiety and depression.
For his two solo albums, Dahl took inspiration from both classical pianist Glenn Gould and jazz pianists like Keith Jarrett, Bill Evans, Cecil Taylor and Bud Powell; cultivating improvisation in extreme situations. There are also clear inspirations from contemporary music and different world regions and folk music.
In 2011 Dahl returned to his drumming roots with the Crazy Constellation Trio, with Hugo Rasmussen on bass and Søren Kristiansen on piano.