[3] Gasser plays large-scale standard repertoire piano works, in particular the Viennese Classics (Mozart, Beethoven and Schubert) and Grieg, Mendelssohn, Busoni, and Rachmaninoff, and the French Impressionists Debussy and Ravel.

His repertoire ranges from Bach's Goldberg Variations to Messiaen's Vingt regards sur l'enfant-Jésus,[4] as well as collaborations with living composers.

Gasser collaborates with contemporary composers and has premiered and recorded compositions by 20th-century composers such as Alfred Schnittke, Ross Edwards,[7] Constant Lambert, Benjamin Britten, Henri Pousseur, Henry Cowell, Toru Takemitsu, George Crumb,[8] James MacMillan, Alistair Zaldua, Michael Tippett, John Webb, James Dillon, Phillip Whilby, Richard Barrett, Cat Hope, Aldo Clementi, Mike Vaughan, John Cage, Luigi Dallapiccola, John Adams, Mark-Anthony Turnage, Olivier Messiaen,[9] Luigi Nono, Edgard Varèse, Judith Bingham, Pierre Boulez, Joël-François Durand, Frank Zappa, György Ligeti and Ronald Stevenson.

Gasser performed Stevenson's Passacaglia on DSCH[10][11] at Carnegie Hall[12][13] as a charity concert shortly after the attacks on the World Trade Center in New York City, to raise money for the families of rescue workers who died in the September 11 attacks, and most recently at the Utzon Room, Sydney Opera House (2012) to launch Yamaha's CFX Concert Grand Piano in Australia.

[14][15] Gasser was a founding member of the Thallein Ensemble and has performed in some of the world's major concert halls and music festivals and has been a soloist with a number of symphony orchestras.