Can someone help me understand this chord progression?

Question

I've been jamming around with a chord progression that goes D F#m C(b5) Bm

The odd chord out is the C(b5), but my ear likes the tension-resolution is creates to end on the Bm. I know there's no "right way" etc, but my understanding of music theory (and a scale search online) tells me this progression is kind of "off" because it's going down four consecutive half steps.

Can anyone help me think about how this is working, whether it does "work", and other chords to use in this harmony?

Thanks, Charlie

Edit: First, thank you so much to people who answered. I know this is the essence of StackExchange but it's so awesome to be the beneficiary of strangers sharing musical knowledge.

Second, someone asked if this is a progression. It does repeat, however it goes

A: D F#m C(b5) Bm

to

B: D F#m Bm (feels a little more "resolvey" without the C(b5).

Answer 1

There are two strong cohesive elements that makes that progression 'hang together'. They all contain F#, and the descending chromatic scale D, C#, Cnat, B. That's plenty to justify a pogression.

Note that the voicing matters. Just plonking the chords down in any random voicings won't sound as good. That constant F# and the descending scale need to be heard.

Here they are, first alone, then contained in larger voicings.

Answer 2

Cb5 could be construed as different things.

1. A voicing of a C7b5 (or Fr+6) chord omitting the 7th (+6th) which resolves down by step to Bm (the vi chord of D major).
2. A tritone substitute for F#7b5/F#+5 (or F#7#11, F#7alt, etc) missing the 3rd which then resolves to Bm.
3. A rootless voicing for other chords, including F#+7 and D9.

The most obvious candidate would be (in my opinion) the tritone sub for F#7b5.

So the analysis would look like:

D: I - iii - subV / vi - vi

Answer 3

In situations like this, it's interesting (and enlightening!) to find other notes which may fit chords in your sequence, without altering the effect much, if any. I found that an A worked well with the C(b5). And in any case, that chord led for me to B major, or perhaps B7.

You call it a 'progression'. Does that mean it loops several times, or it goes somewhere else? If so, where?

With an extra note, it's much easier to understand what might be going on harmonically, as three note 'chords' may not necessarily be what they appear. D F# A looks and sounds like D major, but might be a rootless Bm7, the C(b5) might be part of Am6, part of D9...