 This swing background would allow him to take his music into the realm of Afro-Cuban jazz as part of the Quinteto Instrumental de Música Moderna, which he founded in 1958 alongside Frank Emilio Flynn.He was so highly regarded that during a visit to Cuba by Stan Kenton's orchestra, Guillermo replaced an ill Buddy Rich for one night's performance.Inspired by bop drummers like Max Roach and Roy Haynes, by the early 1950s, Guillermo would organize the Sunday afternoon jam sessions (known as descargas) at the legendary Cabaret Tropicana (featuring stars such as Bebo Valdés), often doing the transcription necessary to explain American jazz music to his band mates to play.