What song is it? I haven't a clue. Who is he? you'd have to ask her. I added the blush and a whole other mysterious level was added to the picture.
I play flute myself so I wanted to draw a Nido playing one too. This was done without without a reference. This flute is actually custom made (or rather, drawn) for Nidorina. Having only three digits (and fairly stubby one at that) on each hand would make it hard for her to play a regular flute, so I simplified it a bit and made it easier for both of us. ;)