Penicuik is on the Lothian bus service 37 from central Edinburgh: singarounds are in the Roadhouse, which is right on the main road (on the right hand side coming from Edinburgh)a bit before you get to the town centre, from 8pm on Tuesdays.

To quote the chorus of Anne Renshaw's much requested song:
The Number 37, it is a braw big bus,
It'll get you doon tae Princes' Street wi'oot a lot of fuss,
It has a bright blue top on it, so you ken whaur it's cam frae,
It's cam frae bonnie Penicuik, by way o' Liberton Brae.

There's also a session in the Grey Horse, Main St, Balerno, on Tuesday 7th from 8pm: no 44 Lothian buses from Princes St (black tops this time!)or First Bus 44 route also.