Born in Barcelona, Spain, in 2005. Since 2019, he studies at the Reina Sofía School of Music’s Aline Foriel-Destezet Cello Chair with Professor Jens Peter Maintz. He also participates in the chamber music chairs lessons under the direction of Márta Gulyás and Heime Müller. He has been granted scholarships by Fundación Banco Sabadell and Fundación Albéniz and plays with a Baroque cello bow, loaned as an instrument scholarship by the latter.

He began his cello studies at the age of 6 and made his debut as a soloist at the age of 13, receiving a completely positive review emphasising a sound ‘of irreproachable quality and musicality’ and an ‘interpretative capacity with a very well-defined personality and his own criteria’ which gave ‘a whole lesson in maturity at the age of 13’. Since then, he has played in some of Spain's best-known venues such as the Teatro Monumental, among others.

In recent years he has won several prizes, including the absolute prize at the MiN International Competition (Narvik, Norway) and first prize at the Certamen de Interpretación Intercentros Melómano. In 2024 he has been awarded at the Bach-Wettbewerb and has won the Primer Palau prize, as well as the critics' prize and the Catalunya Música prize.

In the recent years, he has attended classes by Lluís Claret, Pablo Ferrández and Asier Polo, among others, and has been guest student at the Cello Biennale in Amsterdam.

Guillem performed El Cant dels Ocells with Peter Thiemann on 26 August 2017, at the event in memory of the victims of the terrorist attack in Barcelona.

As a student of the School, he has performed the Brandenburg Concertos with Sir András Schiff and the complete Goldberg Variations arranged for string trio; at the Gran Teatre del Liceu and the National Auditorium of Music (within the Generación Ascendente series); with the Freixenet Orchestra (conducted by David Afkham, Andrés Orozco-Estrada, Péter Csaba, Sir András Schiff and Nicolás Pasquet); the Fundación EDP Camerata (conducted by Paul Goodwin) and the Baroque Ensemble of the School (conducted by Paul Goodwin). He has also been a member of Bain Satie Trio, the Ramales Quartet and the Ambage, Management Solutions Tchaikovsky and Casa de la Moneda Scarlatti ensembles. He is currently a member of the Lili Boulanger Trio.

He plays a cello by François Caussin, Mirecourt Vers 1830-1840.