Gutch, to which key would you like to modulate?
2morrow i have an exam so can't do the chords 4 U now (maybe i'll post next week Mon).
But basically, what U have 2 do is go to the 5th note of the key you are modulating to in your LH & play the 4 chord in your RH..note however that to get a full sound, U include the 5th note in the 4chord being played in your RH...
However, that's just the simplests & cleanest way 2 do it.
U could get to the 5 note on your LH by walking through the 4th while holding the last chord in the key of C , ie.,the C-E-G..Jah...alternatively, U could play a passing chord that fits in, in my mind right now, i imagine a diminished would do (not in front of keyboard now
)
once U've played the 5/ 4chord ,you can resort to the 1 in the new key & c how 2 continue..but the 1, i'm not too sure, but try it.
Since Ur in C, let's say U want to go to F:
The scale of FMaj is F[1], G[2],A[3],Bb[4],C[5],D[6],E[7],F[8 or 1].
So from Jah..C/C-E-G
play the 5 of F scale in your LH, ie C
Play the 4 chord in your RH, i.e Bb-
C-D-F
summary: C/ Bb-C-D-F...,{
5/4-5-6-1 of new key } now U are in the key of F.
Apply formula to any key you want.
Like I said earlier, before you play the 5/4 chord, U could just play: (2),4/holding C-E-G or play a proper passing chord (try D-F on your RH).
Hope this makes sense.