Yes, MODULATION is a Scrabble word!

Letter values in Scrabble US: M 3, O 1, D 2, U 1, L 1, A 1, T 1, I 1, O 1, N 1.

Is it a valid word?

MODULATION is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a musical passage moving from one key to another
(electronics) the transmission of a signal by using it to vary a carrier wave; changing the carrier's amplitude or frequency or phase
rise and fall of the voice pitch
a manner of speaking in which the loudness or pitch or tone of the voice is modified
the act of modifying or adjusting according to due measure and proportion (as with regard to artistic effect)

Also: pitch contour.