I'm sure it must happen but I've not heard singing associated with well dressing, similarly there is no singing at castleton garland. [At castleton, Abide with me and God save our gracious queen are played at the very end round the war memorial - but I can't remember anyone singing - at least not so others would join in or listen to them]
There is traditional music and dance, as Georgina says above, music is usually provided by local brass/silver bands.

Sorry not to be any help with original query.