So lets say I have a grand staff with another treble clef staff for a solo instrument [3 staves in all]. Now where do I place chord symbols for piano? Between the grand staff and the solo instrument staff or on top of all the 3 staves? Thanks
On vocal/piano scores, I've usually seen the chords on the topmost stave. This may be because the chord symbols would clash with the lyrics.
As a piano player, I'd probably prefer them on the topmost stave regardless of the music type. I would warn you that the presence of chord symbols would make me much less likely to play the piano part note for note, and more likely to interpret things and add extra bits.
The chords may also be useful to the soloist, depending on the nature of the piece.
Here are some examples from random scores I have to hand:
And a counterexample:
Note the two vocal lines. Here, it's better to put the chords closer to the actual keyboard part, to make it easier for the player to read.