piano chord
A♭maj9
A♭1C3E♭5G7B♭9
A major seventh with a ninth on top.
Written the other way round it is G♯maj9 — the same twelve keys on a piano, a different piece of notation.
What is true of it
A♭maj9 is A♭, C, E♭, G and B♭ — 1, 3, 5, 7 and 9 counted from A♭.
On an instrument that cannot reach all 5, the 5 and 1 go first, in that order.