Regal Zonophone 2
A few stipulations: Lets keep it to the 60's. (Not that there was much in the 50's, just that I don't like 50s music.) Anything roughly over 6 minutes long, okay? (So I'd accept "Sad-Eyed Lady of the lowLands but not "Like A Rolling Stone" or, say, "McArthur Park" If you can be bothered, please let us know the year/month of release.
chad & jeremy "of cabbages and kings" 1967 has the "Progress Suite"
Procol Harum-In Held Twas I. 1968 17.51 minutes.
BUTTERFIELD BLUES BAND "east-west" 1966
The Who-A Quick One While He's Away. 1967 9.10 mins
"Featuring the Human Host and the Heavy Metal Kids" Hapshash & the Coloured Coat '67 track - Empires Of the Sun (15 min)
SEVENTH SONS "4:00 A.M. AT FRANK'S" track "Raga" (30 min.) recorded '64, released '68
Beach Boys-Heroes and Villains from the Smile Sessions has all sorts of bits and pieces and versions that are well over six minutes.