He was a prolific composer, with some 300 surviving works preserved in more than 10 publications; he was especially important for his keyboard music.
The second organist was Ascanio Mayone, and Giovanni de Macque was maestro di cappella.
Trabaci succeeded Macque in 1614 after the latter's death, and held the post for the rest of his life.
His bold harmonic language, with unexpected modulations to distant keys, and experiments with structure in these works influenced Girolamo Frescobaldi.
His 1602 book of motets, Motectorum, features advanced harmonic writing and may have influenced Carlo Gesualdo's 1603 Sacrae cantiones.