I think the key to the success was musicianship. There were very few "shortcuts" in terms of technology. There were archaic arpeggiators, but not much else in terms of "auto" anything. If you wanted to play something difficult .... you had to actually LEARN to play it. What a concept!
Todays players use lots of auto help to get the sound, and most new music is impossible to perform live. That's not really a bad thing, in itself, but the lack of chops is certainly more evident with todays generation of players.
It's a shame too - these guys are missing out on a lot of fun.
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Every instrument, every voice, every sound in nature ... these are are all my private tutors ... 24/7 for free, and all I have to do is listen.