The Hornbostel-Sachs classification classifies instruments by the way they produce sound. Key-systems or mechanisms can also be used as a criterion. Over the ages flutes have been used in music having several different functions. Therefore flutes can be classified by what they are used for. Instruments for solo playing, consort and band music, for folk music, and for military purposes are made and played quite differently from each other.
Flutes also come in different sizes .