Just a note that my ocarina page is now at

http://www.campin.me.uk/Music/Ocarina/

I mention a couple of recordings there. You could also listen to some of the 1970s Syntagma Musicum recordings of mediaeval and Renaissance music - they used the gemshorn, which is basically the same thing.

I don't particularly like playing countermelodies on it as it's rather too intrusive. Better as a solo instrument.