Fans get another opportunity to dig into Deep Purple's Mk III era with the upcoming release of the oft-bootlegged 'Graz 1975,' long considered the best concert performance ever by David Coverdale, Ritchie Blackmore, Glenn Hughes, Jon Lord and Ian Paice. The show has never been officially released in its entirety.

'Graz 1975,' due Sept. 23 via Eagle Rock, was recorded in Austria almost exactly a year after 'Live In California 74,' which saw reissue earlier this spring. By this point, however, Deep Purple had come to focus almost exclusively on Mk III recordings, only including two songs originally sung by Ian Gillan: 'Smoke On The Water' and 'Space Truckin'. The complete track listing is below.

Unfortunately, that didn't turn out to be a sign of longevity. In fact, 'Graz 1975' chronicles one of this lineup's final shows, as Ritchie Blackmore would exit after just two more dates.

Back together since the early '80s, the band continues with stalwarts Gillan, Roger Glover and Paice, along with Steve Morse and Don Airey. They kick off a North American tour on August 4 in Scottsdale, Ariz., even while work continues on the follow-up to 2013's well-received 'Now What?!'

This year has also seen a deluxe reissue of 1972's 'Made In Japan,' featuring the Gillan-led Mk II edition of Deep Purple.

Deep Purple 'Graz 1975' Track Listing

'The Gypsy'
'Lady Double Dealer'
'Smoke On The Water'
'You Fool No One'
'Space Truckin''