Gould would hold forth on movie scores, on his favorite Sibelius recording (made by Karajan), on astonishing harmonic innovations in Richard Strauss (complete with measure numbers).
Poulenc's music is fundamentally tonal, although he made use of harmonic innovations such as pandiatonicism and chromatically altered chords.
The most commonly cited one is harmonic innovation.
He's best known for his harmonic innovations; as a member of the John Coltrane quartet in the early and middle 1960's, he completely changed the sound of modern jazz piano.
The Fifth String Quartet, startling in its harmonic and formal innovations, is cast in a medium that shuns grandiosity.
His harmonic innovations include movements in which the first section ends in the key of the subdominant rather than the dominant (as in the last movement of the Trout Quintet).
Schoenberg was also one of the first to write on the theoretical consequences of this harmonic innovation.
In rock, harmonic innovation doesn't matter that much.
He studied music in India during the 1960's, and his music reflected many of the harmonic and rhythmic innovations that developed in jazz during that decade.
He also translated the rhythmic and harmonic innovations of be-bop into his compositions for orchestra.