The compromise is, I think, what gives different keys their distinctive colour. For heavily harmonic music there is no question that equal temperament opens up a whole world of possibilities that just temperament would not make possible, at least not with practical choices of instrumentation.Lorenzo wrote:Jerry's scale above seems about right. Notice how the 3rd and the 6th are off about the same in equal. It's because the 3rds and 6ths are related. mathmatically. Peter is right about equal being a compromise. Like someone else said, just is only good for one key. Just makes the F# sound great in D. I prefer the compromise though since I play in about 4-5 keys on the D whistle.
For music that is less harmonically based, just temperament often sounds better. I note with interest that the notes we like to hear a bit flat are mainly the third and the seventh and many of us deliberately vary the intonation of these notes as we play. This is true of blues as well as Irish music. The old (patronising) theory is that blue notes were the result of African Americans used to pentatonic scales lacking the third and seventh having no ear for correct intonation for these intervals. I think that a preference for just intonation and floating intonation is a much more plausible explanation. Variable intonation grabs me in much the same way in both musics.
One interesting thing is that there is a dispute about how well harmony sounds superimposed on Irish music. Not only do blues musicians play and sing modal melodies against the background of pianos, guitars and horns playing full ninth chords and even major sevenths in equal intonation, so too do Romanian gypsy bands use just temperament for melody and equal temperament for accompaniment. Both are an acquired taste and I imagine that if harmony really catches on in Irish music it will be an acquired taste there too. It's still great to hear a blues with little or no harmony though but the tradition is broad enough to allow both strands to flourish. Playing blues you need to make slight adjustments for even intonation, just as you do when playing Irish music with instruments like concertinas.