I sing, and while singing is a valid form of music I don't think that the singing voice counts as an musical instrument as such.

I used to play self taught piano, and there was once a time when I could play with both hands together in harmony. Probably the most complex piece I managed was a simplified version of the Entertainer. I never had proper lessons and anything I learnt was based off the piano books my brother had from his piano lessons.

I did learn flute for two years, wasn't talented though, and because I had borrowed the flute I used at the time, as soon as I stopped learning I stopped playing.