#1
im writing a song in the key of F#, and although C is not in that key, a riff in this song uses a C.
turns out that not only is my riff in the key of F#, but it's also in C#.
so, even though everything up to and including this riff is in F#, harmonies only sound natural when i play them using C#.

is the song not actually in F# or is it both?

i have guitar pro tabs of said riff
#2
Post 'em. It'll help WAY more than words will.
"There are two styles of music. Good music and bad music." -Duke Ellington

"If you really think about it, the guitar is a pointless instrument." - Robert Fripp
#3
Your song can't be in two keys at the same time. It may be that the song is not in the key of F#m. What makes you think it's in F#m?

Also, if it's in the key of C#m, using C natural (or more accurately B#) would be pretty common - it is the leading tone.

But yeah, post it (preferably GP5 or MIDI). We can't tell anything before we hear it.
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Last edited by MaggaraMarine at Feb 3, 2015,
#5
Or Mozart. Or Milhaud. Or Duke.

But yes please post them cuz this is an easy question, and your piece is extremely unlikely to be bitonal.
"There are two styles of music. Good music and bad music." -Duke Ellington

"If you really think about it, the guitar is a pointless instrument." - Robert Fripp