Yes, to expand on what Mike said: if you want to 'name the key,' you may want to think of the A6 as F#m7/A and the Bbmaj7 as A#maj7. Or keep the Bbmaj7 and think of the A6 as or Gbm7/Bbb. Either you'll be dealing with a double flat or double sharp.
Once again, however, these two chords are not in the same key as one another (or the Cmaj7 and Gmaj7). Too many accidentals. It's not modal, just a more colorful (i.e. chromatic) progression you've devised.
If I absolutely had to declare a key (and I wouldn't, because the progression here doesn't really have one in traditional Western music analysis, not unlike the opening of Wagner's "Tristan" prelude), I would probably say G. The C then becomes a IV, the F#m7/A becomes an undiminished vii in first inversion, and the A#maj7 a borrowing from an unrelated key.
|