"Along with Dallapiccola, he was the most significant Italian composer of the mid-20th century"  (Enzo Restagno, Grove Music Online) and he gifted the guitar with two of the most important pieces of the twentieth century for the instrument: Nunc and Suoni Notturni.

"It was in 1971 that he composed his second and final piece for solo guitar, titled Nunc. Dedicated to his life partner, Rosetta Acerbi, it was first performed by Mario Gangi at the Venice Contemporary Music Festival. The same instrumental techniques from the first piece, Suoni Notturni, are used, but as Petrassi himself notes, the novelty lies in the use of percussion. Two types are identified: one is the tambora on the soundboard, and the other is the so-called “Bartók pizzicato.” To understand better Petrassi’s relationship with the guitar, it is interesting to read the composer’s own words in the interview by Ruggero Chiesa, published in 1972 in the magazine Il Fronimo.5
Petrassi confessed that the guitar had always fascinated him and recounted having studied how to compose for the guitar by reading Hector Berlioz’s Grand Traité d’Instrumentation. He never learned to play it himself, but sought assistance from Maestro Mario Gangi, whom he consulted for advice on the two solo pieces. Petrassi acknowledged the difficulty of composing for the guitar and encouraged performers to explore new timbral possibilities to expand the palette of sounds.

“It is difficult for the composer to go beyond certain combinations, while this can happen on the part of the performer, who can discover different things.”

Among the virtues that the composer recognizes in the instrument is its intimacy, and he compares playing the classical guitar to “conversing with a person.” The delicate volume is thus an added value for Petrassi, who does not appreciate the timbre of the electric guitar, which he describes as “detestable.” Intimacy and timbre are further complemented by mystery, which, according to the composer, is one of the most interesting aspects of the instrument. These three elements, combined, give the guitar its unique allure." ( Aurora Orsini, "Goffredo Petrassi and the Guitar" https://www.obiettivocontemporaneo.com/en/2024/07/22)