Born in Calella (Maresme), he began his musical career in a self-taught way, mainly thanks to listening to greats, such as Frank Sinatra, Tony Bennett, Nat 'King' Cole, Ella Fitzgerald and Mel Tormé, and the great orchestras: Duke Ellington, Count Basie, Nelson Riddle...

Subsequently, and after dedicating several years of his career to other musical genres and working in advertising, he began to feel the need to improve his basic academic training and decided to start a university career linked to his other great passion, narrative fiction and cinema. She studied Audiovisual Communication at the Universitat Pompeu Fabra, where she graduated in 1999. During this period he also studied at the New York Film Academy (NYFA).

When this period came to an end, the need to make music resurfaced with force. Unexpectedly, jazz caught his attention, seeing in it an excellent vehicle of musical expression, and that's how he met musicians in this field with whom he worked and learned every day: Emilio Solla, Nono Fernández, Aldo Caviglia, Tom Warburton, Dani Pérez and, later, José Alberto Medina, Federico Lechner, Albert Bover, Jaume Vilaseca, Ben Monder, Oscar Feldman, Ted Poor...

Since then, he has released four albums as a leader. "Yesterday's Sun" (Fresh Sound, 2006), which he presented at the 38th Barcelona Jazz Festival, as well as performing at the prestigious Dizzy's Club at Lincoln Center in New York for four nights. In his second recording project, "Unguarded Smiles" (Quadrant Records, 2010), recorded in New Jersey, he further exploits his facet as a lyricist, something he had already begun to explore in his first CD. On this album, Casellas puts lyrics to music written by great contemporary composers such as Brad Mehldau, Kurt Rosenwinkel or Chris Cheek, as well as to creations from other eras by masters such as Frederic Mompou. He has also performed in different emblematic clubs in New York, such as Smalls, Zinc, Cornelia St. Café and Mezzrow, and national clubs such as Jamboree, Nova Jazz Cava, Milano, Jimmy Glass, Bogui, La Bilbaína and Café Berlin.

His most recent work, "In a Sentimental Move" (Fresh Sound, 2019), also recorded in New York, was born from an impulse to immerse himself in the great songbook par excellence, the "American Songbook", full of beautiful and timeless compositions with which he felt he could develop a deeper expressive search; hence, the choice of the duo format with his colleague and dear friend Emilio Solla, winner of the Grammy for Best Latin Jazz Album 2020. It is a selection of ten universal titles performed in a minimalist and intimate way on piano and voice, which also has solo collaborations with great names such as Romero Lubambo, John Ellis, Julien Labro and John Bailey, which significantly enrich the palette of colors and textures.