In music, a simultaneity is more than one complete musical texture occurring at the same time, rather than in succession. This first appeared in the music of Charles Ives, and is common in the music of Conlon Nancarrow and others.
In music theory, a pitch simultaneity is more than one pitch or pitch class all of which occur at the same time, or simultaneously. Simultaneity is a more general term than chord: most chords or harmonies are then simultaneities, though not all simultaneities are chords.
A simultaneity succession is a series of different groups of pitches or pitch classes, each of which is played at the same time as the other pitches of its group. Thus, a simultaneity succession is a succession of simultaneities.
Similarly, simultaneity succession is a more general term than chord progression or harmonic progression: most chord progressions or harmonic progressions are then simultaneity successions, though not all simultaneity successions are harmonic progressions and not all simultaneities are chords.
- "Meta-Variations: Studies in the Foundations of Musical Thought (I)", p.74. Benjamin Boretz. Perspectives of New Music, Vol. 8, No. 1 (Autumn - Winter, 1969), pp. 1-106.
- Simultaneity in Music by Robert Iolini. Extract from a Master of Arts thesis entitled Simultaneity in Music. Macquarie University. Sydney. Australia. February 1998.