# What is the function of C#7 in the key of D?

I'm trying to understand function of a chord in Miguel Llobet's arrangement of Canço del Lladre. I marked my interpretation of the chords in the excerpt below. The chord symbols in parenthesis are signalized just by a single note, so they are not really played, they are rather the chords I would imagine there to be if I were to harmonize it (though I'm really unsure about G).

My question is about the chord C# in measure 5. It appears to me a dominant chord (I could easily extend it to C#7, or maybe even C#7b9). What is its harmonic function?

By ear I recognize a similarity to diminished common tone resolution, but the played chord is a C# triad, not a diminished one! Perhaps the spelling of F instead of E# is some hint, but I fail to recognize it.

The respective fragment can be found at 0:11 in this recording

• It doesn't sound like C#7, it sounds like a dim chord. It sounds like a C# melody note is being accompanied by a chord progression D/F# - Ddim/F - Em7 - A7. There is a voice leading perspective, with a descending bass F# - F - E. If you make all chord have four notes, it's F#-(D)-A-D to F-D-Ab-C# to E-D-G-B. Didn't we just have a question about something like this, planing was suggested as one possible official world view, maybe tritone substitution or secondary dominant, etc. the same thing as always, "whose subjective perspective gets declared as the real correct only truth". Commented Sep 5, 2022 at 17:35
• @piiperiReinstateMonica hmm, that would make it Domaj7, what a chord! But yes, then it can be then interpret as some form of V/V. Commented Sep 5, 2022 at 18:16
• I tried to say that if we're talking about the sound on the video, the question is based on the wrong assumption, you could transcribe the chord under the melody note as a dim chord, but calling it C#7 is just wrong IMO. And if you want to see it as a V of something, it would be like a V of ii if it's in D, because it leads to Em. But substituting it with B7 doesn't give the same feeling IMO. If you want to see a stack of thirds, then it would be an inversion of a D dim maj7. The guitar isn't playing all the notes at the same time anyway, so it leaves something for imagination. Commented Sep 5, 2022 at 19:11
• @piiperiReinstateMonica I actually found that various recordings vary at this very place, but the way shown in my score is the most frequent. I changed the recording example to Bream's. Commented Sep 6, 2022 at 0:02
• If we leave out the D note from the chord, that changes the canonical stack-of-thirds naming from "D dim (maj7) / F" to "C# / E#". But do you really need a "function", can't you invent your own concepts for your own needs? What does the chord feel like doing to you, what does it seem to do? It leads very nicely to the Em7, doesn't it? Where else could it have lead - have you tried replacing the Em7 with different alternatives? If your role in this is only to mechanically play it, you don't need to know a "function". So I suppose you want to do something more. Commented Sep 6, 2022 at 10:00