From my somewhat limited experience of ITM, it appears that the vast majority of tunes are written in either G Major or D Major and, so far as the fiddle is concerned, can be played in the first position. There are exceptions to this but these are in the minority.
Is there some historical precedent for this I wonder ?
Just interested, that’s all.
Regards to all…Allen
it’s easy… why make things hard?
easy on the fiddle because easier fingerings tha nsay, Bb; and because not changign position is easier than changing position
also easu on the fiddle becasue you can exploit harmonic richness because your notes are closer on teh circle of fifths to the root note of the string (this could be completely wrong as I don’t play fiddle)
easier on diatonic instruments (flute, whistle, pipes, harp-ish, single row box, harmonica, etc.) because you can play everything on one or two instruments… why spend money when you can not spend money?
ornamentation. less use of keys on flute, and less just awkward places on fiddle = easier ornamentation and other types of emphasis on a tune.
D instruments are most common at sessions, so if you wish to play with others, D and G are the keys to be tuned to.
Also, trad music is not traditionally written down. A sort of “habit” has developed where, in order to avoid needing to know any more about written music than necessary, many people write tunes in D or G, but then play them on instruments in other keys, e.g. the fingering on a flute, whistle, pipes, etc. is basically the same regardless of key, so I can take a piece of music written in D and play it on my B whistle, knowing that the fingering will be exactly the same as if I were playing a D whistle, and I only had to learn to recognize the D and G key signatures and notes.
djm
I’d say there’s quite a few tunes in E minor, and a good amount in A minor too. I wouldn’t say the “vast majority” are in D and G. I know at least as many tunes in E and A as I do in D and G.
That’s true, but even then, the key signatures are the same in E minor/dorian and A dorian, whic means the notes played are the same adn the fingerings are the same (generally), so it’s the same idea. “D major” is sometimes shotrhand for “D Ionian E Dorian F# Phrygian G Lydian A Mixolydian B Aeonian and C# Locrian” 
Most fiddle players are pretty dumb to begin with so it is a lot easier to keep it all in the first position.
Slan,
D. 
Yup. We fiddlers are dumb. We only know one position. But I thought it was called missionary. 
A correction: Irish tunes are typically not “written”. Because it’s an aural tradition, a better word would be “composed.” Notated music is merely a bare-bones representation of what is played, and should have nothing to do with the music itself. Other than as a reference, of course.
If you really want to know why tunes are in G and D(and their related minors), research Uilleann pipes. The pipes were “the” instrument after the harping tradition and most of the music today is heavily influenced by them. Heavily.
Bear also in mind that much is written in the key signatures of D and G. It does not follow that that means those are the keys of tunes. Take the Mooncoin Jig, for example: yes, it’s commonly written out in the key signature of D, but it is in fact an A mixolydian tune. There’s nothing D major about it.
Except that all its notes are also in the D Ionian, which is why I can play it on a D diatonic harp. It’s tonal centre may be in A. It just goes to show how simple this music is. I always think it’s a mistake to show a tune like this one as if it’s in D. Better to give a three sharps key signature even though there’s no G sharp in the tune. Or maybe just never write it down at all. It’s much more fun that way.
Yes, one of the major problems in western music theory terminology
is the different meanings for many commonly used terms, overlapping meanings, and hijacking of of useful terms.
The words scale, progression, keynote, mode, absolute pitch, flat and sharp spring to mind.
For instance, the following true statement (which agrees with nano’s point) can become arguable for many unable to distil the appropraite meaning from context and also due to a lack of basic understanding (as well as, often, emotional blocks about words with more than two syllables and sentences that serve multiple purposes):-
Melodies in the mixolydian mode with keynote (or tonic) A are notated in D key signature.
And here are more true and useful statements from a non key signature specific angle that can help in transposing mixolydian mode to different key signatures:-
The mixolydian scale is a heptatonic scale with all intervals just like in a major scale except for the seventh interval which is minor or a semitone flatter than in the major scale. Incidentally, if you take any major scale and (sticking to the notes in that scale) shift the keynote to the perfect fifth interval of that major scale, you will get the intervals for the mixolydian scale. That is why it is predominantly seen relative to the major scale and termed as a mode of the major scale.
Oh no! Now the music majors are crawling out of the woodwork! Somebody please call Pandora and tell her to close her box.
Most of the highland marches/jigs/etc and (as far as I know) all of the piobaireachd tunes are in mixolydian. If I’m not mixolydian my terms that is…
But a little knowledge goes a long way. 
Well, I’m behaving myself this time.
You’d prefer, maybe, music minors? I know quite a few tunes in minor scales. Even a few that start major, go to minor, and the return to major at the fin.