10.37Learn quality by altering one note

Start with Cmaj7:

C E G B

Lower B:

C E G B♭ = C7

Lower E too:

C E♭ G B♭ = Cm7

Lower G:

C E♭ G♭ B♭ = Cm7♭5

Lower B♭ one more semitone:

C E♭ G♭ B𝄫 = C°7

This is a beautiful way to understand the family.

You're gradually darkening/altering one chord.