In Irish music, most of the tunes are traditional, and no one can know who originally wrote them, or in what key they might have been played by the composer.
Moreover, Irish traditional musicians probably couldn't care less.
But I wasn't only thinking about the Irish tradition (this is the whistle forum, not the ITM forum). In the Scottish tradition, thousands of tunes have known composers, all the way back to the eighteenth century. I'll be taking part in an RSCDS workshop in a couple of days - of 79 tunes to be practised, only 21 are 'Trad' - that is, composer unknown. (Of course all of them are traditional in
style.)
Many Northumbrian tunes have known composers, as do many other English tunes, not to mention Welsh tunes, French tunes, and Swedish tunes.
The fact that all these traditions honour their creative talents, rather than preferring to forget which individual wrote a tune, doesn't mean that we have to play their compositions in the keys originally written; of course Gow, or Purcell, or Pigg, or Jonasson, aren't going to turn in their graves if we play their tunes in a different key. But there
was an original key.
Granted, the keys we have today for Carolan tunes reflect performers' preferences at the time those tunes were published, long after Carolan died. But the whole concept of key signatures was around long before Carolan was born: Dowland and Byrd wrote in specific keys - or if that seems a little too grand, Playford's Dancing Master 1st edition in 1650, 20 years before Carolan was born, has quite a variety of key signatures (but nothing for the E flat whistle).
So I come back to my original question - apart from just playing everything you would normally play on a D whistle on an E flat whistle instead (and of course you can do that), are there any tunes actually written for that instrument, or any that sound really good on it?
but if i ever do make it down there to a session i'll be sure to bring my Eb; thanks for the head's up. 
