It would need to be song that would go out of tune in about 3 minutes (as my harp does in hot, humid weather). It's awful to be in the middle of Rakes of Mallow and suddenly find the f# is now closer to f natural.

Irish/Scottish music doesn't deal a lot with heat and humidity, but you'd think there would be more songs with the word "rain" featured prominently. How about Mountain Dew, Foggy Dew, or A Walk in the Irish Rain.