Space plays and stops
- Notes and intervals
- A#M3C##m3E#m3G#
A# Dominant 7, written A#7, is built from A#, C##, E# and G#: the root, major 3rd, 5th and minor 7th.
Its 3rd and 7th, C## and G#, are its guide tones: they say what kind of chord it is, so voicings are built around them and the root is often left to the bass. E7, a tritone away, has the same two notes the other way up, so it can stand in for A#7 as its tritone substitute.
In the progressions here, A#7 is the III7 of the Cycle of Dominants in F# and the VII7 of the Coltrane Changes in B.