Q: or something else entirely?
A: it's that, but i'd say you have to skip the Eb note in the Abmaj7, to give the melody room to do C D E. and the last chord.... i hear A in the melody, F in the bass, i also hear D, and it feels crunchy in a way that Dmaj/F would feel. Without opening it up, that's my best guess. Okay, i've opened it, and i was right. and it's also worth  noting that actually none of the maj7's have their 5 notes in them. Also, plot twist now, there is more to the puzzle: in addition to the harpsicord (playing the chords) there is also a bell playing these single notes on each chord: D, A, C#, G#. so the Bmaj7 is in fact more like Bmaj9, the Ab chord is now extremely illegal (although the meat of the bell note can't really be heard, so it doesn't seem to disturb the harmony, surprisingly. only its twinkle seems to be audible), and the final G# just intermingles with what was already a crunch chord