aikakone, I used to play bass in my younger days. I wasn't very good at it but still had a fun time learning and experimenting.
When you mentioned the 12th fret octave/energy subject, that took me back to the person who inspired me to play, Gary Thain, a Kiwi musician who played in Keef Hartley and later, Uriah Heep. Although the Heep was critically slagged, and in most cases rightfully so, have a listen to this man play. He was originally a jazz player and he played off of the twelfth fret like a madman. His style sounds way too busy for my ears today, but his talent is undeniable. Try the albums Uriah Heep Live or The Magician's Birthday. He always played a Fender Precision, which had a REAL long neck, making his dexterity all the more amazing.
Years later, I came to appreciate the more restrained and complementary style of players such as Ron Blair (with Tom Petty) and of course, Nigel Griggs.