It all depends on how you use it...i dont think that some german house Dj bangin out 'choons' is really using it as an instrument, but more a catalyst. However, if you look at the turntablist use of turntables, scratching,juggling,drumming, needle dropping and using things like loop stations then i would most certainly consider it an instrument, because instead of just playing someone else's music, the person is using the turntable to create a unique sound...or loop etc...