This would be my list of 30 bands (RANKED!) meeting the following criteria
a) Founded in the late 60's or early 70's
b) In some sense progressive - expanding the musical language of popular music or experimenting
c) Had some longevity - at least four albums
d) Bands not solo artists
e) Ignoring erm problematic ideology - looking at you Magma
1) Henry Cow
2) Magma
3) Captain Beefheart and the Magic Band
4) Can
5) Velvet Underground
6) AMM
7) Third Ear Band
8) Faust
9) Kraftwerk
10) Soft Machine
11) King Crimson
12) Incredible String Band
13) Yes
14) Black Sabbath
15) Mothers of Invention
16) Embryo
17) Area International
18) Plastic People of the Universe
19) Amon Düül II
20) Heldon
21) Kluster/Cluster/Harmonia
22) Ash Ra Tempel
23) Gentle Giant
24) Cos
25) Floh de Cologne
26) Van der Graaf Generator
27) Mahavishnu Orchestra
28) Tangerine Dream
29) Guru Guru
30) MEV (Musica Elettronica Viva)