Porcupine Tree does not refer to a strange type of tree! It's the name of a very good, if mostly unheard of rock band which originated in Hemel Hempstead during the 80's. They describe themselves as having "managed to defy genres and blend together numerous ambient, rock and avant-garde styles to create a musical landscape that is both refreshing and compulsively seductive." They've released 10 studio albums and are well worth investigating!
The cache can be found by applying the numbers used in a selection of their songs to calculate the coordinates. They should be easily found with some gentle internet searching!
1. How many chords would make a million? = A
2. Which LSD Voyage did Brian meet himself coming down the up-staircase? (The effect was crushing!) = B
3. How many Recurring? = C
4. How many Cats danced on the moon? = D
5. .? = E
The final coords can be found at -
N 51. A5.5A(Ex2)
W CCC. (B-6).(D-2)11
You can check your answers for this puzzle on Geochecker.com.