Chords to a Bassline

Let’s follow the thought processes of chording this phrase.

Chord 1.

The first bass note is C.
The note directly above C is G, the 5th of C.
The chord is C something.
The notes above the bass note are G, E, C, Bb and Db.

D.S (C) =CDEFGABC  
 C   G    = C (no 3rd)
 C E G    = C
 C E G Bb  = C7
 C E G Bb Db= C7b9

Chord 2.

The second bass note is C#.
The note directly above C# is G, the b5th of C.
Check to see if the chord is C#dim or C#m7b5.
The notes above the bass note are E, G and Bb.

D.S (C#) =C#D#E#F#G#A#B#C# 
 C#   G   = C#b5 (no 3rd)
 C# E G   = C#mb5
 C# E G Bb = C#dim

Chord 3.

The third bass note is D.
See how the bass line is moving up in semitones. That kind of writing always sounds great.
The note directly above D is A, the 5th of D.
The chord is D something.
The notes above the bass note are A, C, A, F and D.

D.S (D) =DEF#GABC#D 
 D   A   = D (no 3rd)
 D F A   = Dm
 D F A C = Dm7

Chord 4.

The fourth bass note is D.
The note directly above D is Ab, the b5th of D.
Check to see if the chord is Ddim or Dm7b5.
The notes above the bass note are Ab, F, B, Ab and D.

D.S (D) =DEF#GABC#D 
 D   Ab   = D(b5) (no 3rd)
 D F Ab   = Dmb5
 D F Ab B = Ddim