Another vote for the Plugged Nickle sessions.
and I'd be remiss in not mentioning the Box Set "Bill Evans - Secret Sessions".
when Bill Evans played the Village Vanguard some guy would always
bring his tape deck and record from the audience. Mid to late 60s I think,
and I'm not sure of his equipment. But the Evans estate (or someone)
got hold of the masters and released them as a boxed set on Verve.
not as stunning as some period auds I have heard in terms of sound
quality, but you gotta give the guy credit, he recorded a bunch of
shows at the Vanguard over a span of like 8 years, and it was ultimately
released by a major label. although the sound quality may be lacking,
some of the music is phenomenal.
there have been a bunch of 60s auds (& boards) circulating over on
easytree,org for Coltrane, Miles, Pharoah, Ornette, etc. lately of varying
degrees of quality as well.
too bad they didn't have access to the kind of equipment then
that we do today.