The vein of nostalgia runs deep. Deep Purple — the ’70s (actually, they’ve been around since ’68) band that, to a large extent, invented heavy rock, survived more line-up changes than the Liberal leadership, and whose lead singer is now of official retirement age, yet shows little signs of fading to mere mauve — is currently engaged in a gruelling tour that takes them well into October. It’s the kind of schedule that could knock many younger men, or women, flat.

It’s easy to don the cynical suit and carp, “they’re not the same without Blackmore and Lord”. But the fact is Lord was more or less forced to retire due to injury and Blackmore, for all his stupendous talent, seems to emerge as a cantankerous old bastard, so for sanity’s sake the body corporate is probably better rid of him. Then again, it’s like speculating on what the Queen is really like behind closed palatial doors.

This week’s Purple features the rhythmic backbone of Ian Paice and Roger Glover, and the superlative, surprisingly subtle vocals of the singer who brought the most success, Ian Gillan. Gillan’s voice is so perfectly formed and sports such a warm, wonderful timbre, Sir Andrew Lloyd Webber saw fit to cast him as Jesus for the seminal English cast recording of Jesus Christ Superstar. Sure enough, vocally, he walked on water then turned it to wine.

There are enough twists, turns and blues in the Purple plot to draft a Spinal Tap-meets-Neighbours (well, East Enders or Coronation Street) comedy-melodrama. One interesting sidelight I happened upon involves the original singer, Rod Evans, whose contribution and quality is not to be underestimated and who arguably made the vocal mould into which Gillan later slipped so easily. While Evans really helped get the ball rolling with the likes of a psychedelic take on the Joe South song Hush, not to mention the unlikely hit with Neil Diamond’s undeniably raunchy Kentucky Woman, he appears to have been very much sidelined after.

So much so that when, in 1980, he made a move to cash-in on the brand he helped consolidate, touring under that moniker with a bunch of session musos, he was slammed by his former band-mates and lost $672,000-odd in court. He hasn’t been heard from since and one suspects he might’ve died from chronic embarrassment. Ironic, then, that one of the highlight’s from this week’s Sydney Entertainment Centre (the acoustics will only ever be righted with TNT) concert was a lovingly crafted replication of the rather tricky studio production sound of Hush.

Ritchie’s website recounts his departure, mid-tour in ’93, was due to his disappointment in Gillan’s performance. Since, Blackmore has been dabbling, presumably, in Arthurian daydreams and dark arts, as well as something called Blackmore’s Night, which seems to embody his penchant for ancient Celtic fare.

The real question is, though, can Purple still get it up? Emphatically, yes. I say this not out of any duty-bound allegiance to teenage idolatry, or surrender to hopeless nostalgia for the circa-’75 show I attended at the Pavlova, but as a result of scientifically detached, forensic audio examination of the evidence. Their new material has the goods to see it incorporated in the legacy Purple must one day leave, if ever they should retire. This, without Lord or Blackmore. Again, who would’ve thought? It seems like some kind of sacreligious disloyalty akin to Judasism to even contemplate it, but there you have it.

Having said that, it’s bloody hard to look past the visceral thrill and thrall of Space Truckin’. Speaking of which, when, not if, Hawking’s well-travelled, acquisitive aliens arrive in their giant craft to colonise earth and, hopefully, save us from a climatic fate worse than death (god only knows Big Kev never will, let alone his nemesis, the Archbishop of Canberra), we needn’t be equivocal in placating them with a classic example of the rock upon which human culture is built. It’s colour will still, incredibly, be Purple.

The details: After shows in Brisbane, Sydney and Newcastle, Deep Purple plays Canberra tomorrow, Melbourne on Sunday, Adelaide on Monday and Perth on Wednesday. Some tickets remain for Melbourne and Perth through Ticketmaster.