What is the difference between Cm7 and Eb/C?

Question

The other day I was looking at the song "On Green Dolphin Street". For the first line there have been the following chord-symbols:

Cmaj9 - Eb/C - D/C - Db/C

As far as I know, the slash-chords are meant to be read this way:

[chord]/[basstone]

So the second chord (Eb/C) is an Eb-major triad with a C in the bass (C - Eb - G - Bb). That are the same notes a Cm7 is made of.

So if my previous suggestions are correct, the question is where the difference between these two notations is. Should I approach these symbols differently?

First I thought that for the Cm7 I would use the c-minor blues scale for improvising and for the Eb/C I would use the Eb-major blues scale. But they have the same set of notes, so what's the difference?

Answer 1

I read the "Eb/C - D/C - Db/C" like, "bass stays at C and piano or guitar or whatever can play these chromatically descending major chords, in order to produce essentially the kind of barebones accompaniment that the composer or arranger had in mind."

Eb/C creates a Cm7, but spelling out the Eb, D and Db is a helpful hint for seeing how you can or perhaps even should look at it. It might also make some players play the chords with a bit more open voicings, not cramming all four notes of the Cm7 together inside one octave, but dropping the C to bass.

You could also take advantage of the chords written as Eb - D - Db by outlining or arpeggiating those triads in your solo? Why not even dissect the Cmaj9 as something like Em/C or Em7/C or G6/C? More possibilities for outlining chords as arpeggios.

Chord symbols should be seen as guidelines for accompaniment, not as theoretic harmony specifications for feeding into a musician-guidance autopilot computer that calculates the "correct" scales to use. :)

You can read and write chord symbols in many different ways, like:

• a pianist can play the thing before the slash with her right hand, and the thing after the slash with her left hand
• guitarist plays the thing before the slash, bassist plays the thing after the slash
• that's how the composer or arranger thought of it, separating a bass movement (or pedal tone) from stuff happening higher up

As a player and improviser you're supposed to understand the bigger picture, i.e. what it all sounds like when put together as accompaniment to the melody. Make up your own mind as to where the harmony could lean on at each point, and where it seems like going to. I kind of like the attitude that you shouldn't try to spell everything out and spoon-feed particular exact harmonies to jazz players who are supposed to be able to improvise their own arrangements on the fly. How often is it actually necessary to write a maj9, and a maj7 wouldn't be enough to deliver the essential idea, letting the players add 9ths and whatever seasoning they want? Isn't that like listing each individual note where a guitarist should use vibrato, and if he should pick with an upstroke or downstroke? :)

Answer 2

C - E♭ - G - B♭ = Cm7.

E♭ - G - B♭ - C = E♭6.

Cm blues scale uses the same notes as E♭maj blues scale.

So, either (or both) as they use the same notes, will obviously work! As will, in fact, all the rest of the notes in the chromatic scale, if you know how and where they'll go!!

Green Dolphin Street uses a sort of C pedal effect, so obviously in this tune, C will be regarded as the root rather than Eb (or any other). Or, looking at it another way, there's a chromatic drop from E♭ back down to the root, C. So it really doesn't make any difference, only where in the bar you put the notes you feel you want to emphasise - for starters, beat one - but not necessarily...