I loved West Cork on my recent trip there (almost as much as Connemara, which I fell completely in love with), and particularly Mizen Head. Stayed at a magical place in Schull, and really enjoyed it - although I tried hard to track down music in the town and couldn't find any! was in September, though, and I had the impression that there's lots in summertime. Never saw a planetarium there though - will have to find that next time.

The beach at Barley Cove was gorgeous, though wouldn't call it deserted - a few people when I was there, plus a hotel and chalets on the hill above it.

Had a very special time on the peninsula.

Here are a couple of good links:
Singers sessions in Ireland
Mudcat thread I started for my trip this year