OK, no Irish or Scottish content here whatsoever, but I saw a really memorable performance a few weeks back. CityMusic brought the Bulgarian State Television Female Vocal Choir to Columbus earlier this month. I first encountered this group's recordings in college, shortly after they were released. The singing is just astonishing: Filled with six part harmonies, noises, talking, pitch bending, dissonance, unusual time signatures, and a laundry list of other things which would be a train wreck if attempted by lesser performers, it's some of the most beautiful vocal music I've ever heard.
You can hear samples of the recording I have on this Amazon.com page.
The opportunity to see this ensemble live was especially nice because although the CD recording I have includes incredible feats of singing, the audio quality is not that great. I recommend the CD for the unusual and brilliant singing, but don't expect great fidelity.