Slash Chords - Part 2
Descending bassline starting with minor or minor 7th chords
Dm → Dm/C
Let's have a look at the following chord progression with descending bassline:
To change the Dm to a Dm/C, we have to replace the root D in the bass by a C.
It would be correct to call this new Dm/C chord a Dm7/C, because the new bass C is the 7th of Dm. But nomally we can ignore the function (interval) of the bass tone in the chord name on the left side of the slash. Writing Dm7/C is usualy done for a different reason...
B half diminished (Bm7b5) can also be seen as Dm/B. That means only the bass tone is moving in the first three bars.
Dm7 → Dm7/C
Now starting from a minor 7th chord:
Again the same thing is happening. The root D is going to be replaced by a C. But when we take a closer look at the resulting chord shape, we see that there is no more D at all in the chord!
Strictly speaking our new slash chord is not a Dm7/C, but F/C - a F major triad (with the tones F, A and C) over C in the bass.
In practice we are just looking at the descending bass tone and therefor we name our slash chord in a way that instantly makes clear what you have to do on your guitar rather than trying to be too precise.
We are writing Dm7/C, because the chord has derived from the preceding Dm7
(even if there is no more D in the entire resulting chord).
It's not always about the most possible accuracy. The goal is to make a player reading fast and not to play needlessly complicated.
Starting from minor, but descending via the maj7
Dm → Dm/C#
If we lower the bass note of the Dm chord by just a half step (from D to C# - the maj7 of Dm), we should lower all D's in the chord to C# (otherwise is may sound terribly dissonant). Now the resultng chord is actually an augmented C# chord (C#aug or C#+). Got it? Not quite clear? Ok, that's why we prefer writing Dm/C#. Coming from Dm you will instantly know what to do (your playing experience will tell you), even if the chord symbol is not really completely correct.
Example chord progression
Actually the same, notated even more correct - but relatively complicated, isn't it?
Finally you can use both variants. It probably takes some time and experience to always chose the right chord name for each harmonic situation.