On the first poem of his book Songs of Innocence and Experience, William Blake wrote:
Piping down the valleys wild,
piping songs of pleasant glee,
on a cloud I saw a child,
and he laughing said to me:
'Pipe a song about a Lamb!' (...)
According to the context and some googling, piping could be playing the flute, but I'm in doubt, cause it seems to be a voice-singed song.