Piano players use rootless voicings a lot of the time. Guitarists tend to learn chords with the roots in. Possibly it’s easier for piano players, who can add the bass in the left hand, when there is no bass player.
You can get a lot more colour out of four note chords if you leave out the root and add a ninth. And you probably already know the chord shapes by a different name.
Here’s an example: Cmaj7 is CEGB.
Leave out the root and add a ninth, and you get EGBD. “But wait!” you say. “That’s Emi7”. Well, ask a piano player and they’ll probably view EGBD as Cmaj9.
So wherever you see Cmaj7 you can probably play a nice Emi7 voicing and it will sound great.
Any maj7 chord can be replaced by the mi7 chord build on the note a third up:
- Cmaj9 = Emin7
- Fmaj9 = Amin7
- Bbmaj9 = Dmin7
Here’s another example. Amin7 is ACEG. Leave out the root and add a ninth, and you get CEGB . That’s Cmaj7.
So any min7 chord can be replaced by the maj7 chord build on the note a minor third up:
- Cmin9 = Ebmaj7
- Fmin9 = Abmaj7
- Bbmin9 = Dbmaj7
You probably know this one: C7 is CEGBb. Leave out the root and add a ninth and you get EGBbD. That’s EØ. Or add a flat ninth, you get E G Bb Db. Thats Edim (or Db dim, Gdim, Bb dim)
Finally Amin/maj7 is ACEG#. The rootless voicing would be CEG#B. Thats Cmaj#5. This sounds well weird.
- C9 = EØ
- F9 = AØ
- Bb9 = DØ
- C7b9 = Db dim
- F7b9 = F#dim
- Bb7b9 = B dim