Finland is pretty renowned for their music scene and holds tons of music festivals. Belgium has alot of music fests and so does Sweden. Below is a list I had b/c I once wanted to hit the music scene on a trip across Europe. I still do but it's back down on the list now

I think some of the Jazz fests would be super cool to check out. If you happen to be into Jazz & Blues music,
HERE's a list of tons of fests and
HERE'S another list all in July. HERE"s a list of 2008 psytrance festivals in Europe. Best to hit the music scene in the summertime!
When do you plan on taking your trip buzzworthy?
Brussels Jazz Marathon- May 14-16
Hultsfred Festival, Sweden-June 12
Provinssirock, Seinäjoki, Finland-June
Couleur Café, Brussels-June 25-27 (Caribbean, African, Latin American and more)
Montreux Jazz Festival, Montreux, Switzerland-July
Roskilde Festival, Denmark- July 3- it's mainly heavy metal and punk
Rock Werchter, Belgium-July 3
Oxegen Festival, Ireland-July 11
T in the Park, Scotland-July 11-13
Pori Jazz-Pori, Finland July 11-19 (44 years so far!)
Stockholm Jazz Festival, Stockholm, Sweden-mid July (this one would be awesome to go to!)
Benicassim Festival, Spain-July 17
Salzburg Festival,Salzburg, Austria-July through August (classical) I'd love to check this one out!
Esperanzah! World Music Festival, Floreffe, Belgium July 30-August 1-this one seems very cool!
Ankkarock, Greater Jelsinki area- August (tons of different bands)
Sziget Festival, Budapest-August 12
Koneisto-festival, Finland-August (electronic)
Pukkelpop, Belgium-August 14