He collaborated with leading American soloists, such as Anthony Braxton, Steve Lacy, Don Cherry, Roswell Rudd, Max Roach, but also with the Argentinian Gato Barbieri and Frenchman Jean-Luc Ponty.

He also adapted the compositions of Albert Ayler and Sun Ra for solo piano, which the Soul Note label issued.

From 1991 to 1995, Gaslini composed works for Carlo Actis Dato's Italian Instabile Orchestra, and was the first holder of jazz courses at the Santa Cecilia Academy of Music in Rome (1972–73).

As to contemporary music, he composed symphonic works, operas and ballets represented at the Scala Theatre in Milan and other Italian theatres, in addition to film scores, including Bali (1970), Your Hands on My Body (1970), Cross Current (1971), The Hassled Hooker (1972), The Night of the Devils (1972), So Sweet, So Dead (1972), When Women Were Called Virgins (1972), Five Women for the Killer (1974) and Kleinhoff Hotel (1977).

Gaslini died at 84 in Borgo Val di Taro, in the province of Parma, where he had been living for years together with his longtime wife and 14 dogs and cats.