Chord progression, how to add the bass properly

Question

I'm really a newbie and self-taught, so I beg your excuses in advance for a poor question. I'm following a course in game programming, and I come out with this progression that IMO should work as a pad for a SCI/FI ambient:

Dm-C-Am-Fsus2/C

The last chord is written that way because it is voiced with C as the bass note. I don't know if it is correct--I hope it is.

The progression first was played with simple triads, and then I decided to add a bass. The bass line was at first D-C-A-F. But this way, the progression "tastes" differently. I tried play it D-C-A-C, where the lower note of last chord is C instead of F. I supposed that the bass should play the tonic of each chord, but it seemed to work better with the lower note (C). Which of these two choices (C or F) is theoretically correct?

Then other question--if I were to write this progression with Roman numerals, since I'm in key of D, I would write: I-VII-V-? What do I put in place of the question mark? How do I show with Roman numerals that I'm using a suspended chord?

Answer 1

In addition to Laurence's fine answer, I would add that there isn't a strict requirement that bass must always play the root of a chord. For example, when playing a major chord, it's common to hear the bass play the third or the fifth instead of the root. For instance, if the chord were Cmaj, you might hear the bass play C (the root), E (the third), or G (the fifth). These are all theoretically acceptable and correct.

I agree with Laurence and others that this final chord is very likely a Csus chord. Ultimately, though, I think it depends on where you hear the chord resolving. If you hear the F resolving down to an E (a 4-3 suspension), then it's a Csus chord. If you hear the G resolving up to a A chord (a 2-3 suspension), then it's an Fsus/C chord. This just might be a theoretical exercise, although it might not be. If you decide to incorporate a later section which begins right after the Dm-C-Am-Fsus2/C progression, then the difference between Csus and Fsus/C could become relevant.

At any rate, for the purposes of your second question (the Roman numerals), let's assume it's a Csus chord. I tend to hear the tonic of this progression as being Cmaj (or maybe Amin), but not Dmin. However, we can write the progression a few times, assuming different tonics.

• the progression is: Dm-C-Am-Csus
• using Cmaj as the tonic: ii-I-vi-Isus
• using Amin as the tonic: iv-III-i-IIIsus
• using Dmin as the tonic: i-VII-v-VIIsus
• using Fmaj as the tonic: vi-V-iii-Vsus

(We use uppercase Roman numerals for major chords and lowercase Roman numerals for minor chords.)

I think writing out "sus" after the Roman numeral clearly communicates what you want to say. Another option is to spell it out completely (I54 for Isus4, III54 for IIIsus4, etc.). user19698 describes that in this answer.

Answer 2

By calling the chord 'Fsus2/C' you've already chosen the bass note. If the bass note wasn't C, it would just be 'Fsus2'. It is 'theoretically correct' to play 'Fsus2/C' with C in the bass because 'Fsus2/C' MEANS 'Fsus2 with C in the bass'!

As mentioned in a comment, it might be more useful to call it 'Csus'. But we're only arguing over labelling. If you like the sound 'C, F, G' it doesn't really matter what you call it. There are no rules that 'allow' certain notes or chords, though 'theory' can (sometimes) put a label on a formula which has proved successful in the past, and help you reproduce it.