Alice,I just had another enjoyable surf aroudn the Txistuaz website (address above in the posting by GUEST, i.e. me). I still love it. These three tunes sound really good on the high sounding whistle: Bakartegia, Pasaian, and Gipuzkoarra. They are near the end of the second set of tunes on the page. There are others there too - I didn't listen to them all, but Bakartegia is one of my favourites from that site. I hope you know some other whistle players who can play the counter melody lines - it would be sad to only be able to play one line.
Helen