1The fourth falls, or floats
V in A♭ majorEb7sus4 is a dominant with a fourth where the third would be. In older styles the fourth falls a half step and the chord becomes Eb7; in modern jazz it often stays, and the sus chord resolves to Abmaj7 as it is.
Listen for: The fourth falls a half step to the third, which holds over the barline as the major seventh of the I.
