This is a hard task Architect. My list is changing all the time but I'll post ten just to play along.
1. Ludwig Van Beethoven (I have well over 100 CD's of his works)
The others are in no particular order of preference.
2. Rush (I think they have done one of the greatest bodies of work in rock music history)
3. Jethro Tull (I'd match his creativity and legacy against any of their peers and think they can hold their own easily)
4. Kansas (A hugely important and influential band for me growing up, their first 8 records are excellent.)
5. Deep Purple (Another fantastic band with as many lives as Rasputin, and still going strong.)
6. The Beatles (Will always hold a special spot in my heart, part of my formative years when I discovered rock music.)
7. ZZ Top (What can I say, their early years are essential to anyone's rock library, and I even like their MTV era stuff.)
8. Pink Floyd (Totally unique and cast a giant shadow for decades.)
9. Yes (Legends who have kept prog rock alive forever seemingly.)
10. Gamma Ray (A band I found by accident years ago that rekindled my enthusiasm for new bands and got me interested in collecting again.
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