Other than the Maj7, what other chords can create others by altering only one note?

Question

So I have done this great exercise where you alter one note at a time to create a new chord:

    Cmaj7   C   E   G   B
    C7      C   E   G   B♭
    Cm7     C   E♭  G   B♭
    Cm7♭5   C   E♭  G♭  B♭
    Cdim7   C   E♭  G♭  B♭♭

This really helps you visualize how chords are made, so I wonder what other chords can you start with to do the exact same exercise?

Answer 1

Don't forget about the basic triads! But in order for your particular system to work, you'll have to start with either the augmented or diminished triad:

    +    C    E    G♯
    M    C    E    G
    m    C    E♭   G
    °    C    E♭   G♭

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Also, note that, with one small adjustment, you can string some of these together to just keep going through all chordal roots. As one example:

    Cmaj7   C   E   G   B
    C7      C   E   G   B♭
    Cm7     C   E♭  G   B♭
    Cm7♭5   C   E♭  G♭  B♭
    Cdim7   C   E♭  G♭  B♭♭
    Cm7♭5   C   E♭  G♭  B♭ (return here to keep the one-half-step rule)
    C♭maj7  C♭  E♭  G♭  B♭ (enharmonic to Bmaj7)
    B7      B   D♯  F♯  A
    Bm7     B   D   F♯  A
    Bm7♭5   B   D   F   A
    Bdim7   B   D   F   A♭
    Bm7♭5   B   D   F   A (return here)
    B♭maj7  B♭  D   F   A

And so on.

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Otherwise, it seems you could do this half-step exercise with pretty much every extended tertian chord (9ths and above), since you can always explain something as, e.g., ♯11 or ♭13 or add9.

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I've also taken the liberty of editing your Cdim7 to use B♭♭ instead of A. In short, since that pitch is the seventh of the chord, we want to spell it as the note a seventh above C. Since a seventh above C is B, we want to spell that pitch as some type of B—in this case, B♭♭—even though it's enharmonic to A. When we spell it as A, we actually create an Adim7, since the thirds of A C E♭ G♭ stack with A as the root.

Answer 2

Here's an example with 9 chords.

Answer 3

What about something like this?

C E G (C major, of course) B E G (E minor, inverted) B D G (G major, inverted) B D F# (B minor)

... and so on.

This sort of thing might help you compose, because you will know which chords are really close together, if the passage requires something like that.

Answer 4

One common contrapuntal technique is to take a chord like C-E-G and change to a C-E-A; it's called the 5-6 technique by some authors. (Bach liked this technique apparently.) Obvious other examples are just taking C-E-G and making C-Eb-G (thence to C-Eb-Ab creating movement down four flats by only making two chromatic tone changes.)