Jack - you might try contacting Nanne Kalma, who certainly speaks and sings in Friesian and used to run and teach several bands. Here's a contact page for him: Nanne (email at the bottom). (He's been over here several times and his English is excellent - you don't need to communicate in Friesian. He's also very into Esperanto - recorded songs in it!). Say hello from me if you contact him.

Mick