Bruce Brodeen wrote:

And it makes me think of a possible strain. Five bands from 
folks' earliest of music listening 'careers' that forever 
changed, shaped, molded, influenced and enhanced your life, 
putting you on the road to ridiculous expenditures on 
music. A bit nebulous, but possibly fun and simple one w/o a 
lot of thought as it's almost an instinctive response for 
most.

Sorry but five is not going to cut it so how about the Big 
Ten, in chronological order:

The Bee Gees + Bread
Before the Fab Four made their full impression on me, it was 
big ballads in the back of me Dad's car (8 track rules!)

The Beatles
Nuff said.

Deep Purple
My first band played "Smoke on the Water" incessantly! Did 
everyone who grew up in the 70s?

Pink Floyd
From the moment I heard that opening sequence to "Time," I 
was hooked

ELO
New World Record was the reason and I remain a Jeff Lynne fan 
to this day.

Queen
Frankly untouchable in the 70s, such eclectism. Progressive 
pop in the true sense of the word.

Genesis
Banks, Collins, Gabriel, Hackett, Rutherford - what a 
combination of true artists!

The Jam
Never liked the Pistols or the Clash, Weller and co were the 
real deal for me...(they LIKED the Beatles)

XTC
Quirky pop genius that got better with age...

Bubbling under:
The Police, Bowie, Elvis Costello, U2, Beach Boys, Neil 
Young, Todd Rundren, KISS, Replacements, Stones et al.