Pipers communicated tunes to each other by diddling or canntaireachd.
Travellers usually came back to their home area in winter. Many Travellers were good pipers, and when they met up they would talk about the tunes they had heard on their travels. They played by ear, and didn't write music, so they communicated the tunes by canntaireachd or diddling. Even the greatest pipers, the MacCrimmons, communicated new tunes in this way. Among the Travellers, the girls would dance to diddling, and the steps they made corresponded in some way to the fingering the pipers would use on the chanter. Duncan Williamson diddles.