To build a major + minor chord on the key board
major= count 4 semitones from the first note and then count 3 more after for a major chord
minor= the opposite way round 3 and 4
For a major seven it is 4, 3 and 4
For a minor seven 3, 4 and 3
For a dominant seven its 4, 3 and 3
To add 9 you would use 4 for major 3 for minor
For a diminished chord you must count 3 semitones so if you start from C your first note is C then D# then F# then A The most direct scale to play over a diminished chord is the octatonic( meaning diminished) scale which is built alternating between whole and half steps one after the other (half tone is a semitone and a whole tone is 2 semitones)
For example for an A diminished chord you could use the A diminished scale with notes consisting of A-B-C-D-Eb-F-F#-G.
If you change to root on a chord which is the bass note to a note within the chord it will change the chord and make a slash chord which is like D/F# or in half the world away the chord go from a C then changes the bass note to make a C/B then to a A minor to make the walk down also the Beatles did it in while my guitar gently weeps around the A minor
I started building a chord progression on the keyboard using chords G,E and F then I plan to add for the chorus to consist of the chord C and notes around it. I then added
