create implication singing -> music
create implication playing_instrument -> music
create implication playing_instrument -> instrument
The wiki page for Music says to "Use this tag whenever a character is playing an instrument or singing." Thus when someone is singing or playing an instrument this tag should be used.
Also, when someone is playing an instrument there is an instrument being played.
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On a side note (no pun intended) is there any purpose to the song tag? It seems to be overwhelmingly used for music videos, with a couple of sets of lyrics thrown in, both of which have their own tag that captures what is present considerably more effectively.