Deep Purple Mark I's Nick Simper believes his lineup of the band withstood a level of pressure that none of the later editions had to face when they released three albums in the space of 16 months.

Singer Rod Evans and bassist Simper were dropped in favour of Ian Gillan and Roger Glover in 1969, 16 months after the band had been formed with Ritchie Blackmore, Jon Lord and Ian Paice.

Those first three records – Shades Of Deep Purple, The Book of Taliesyn and Deep Purple – have been collected in a 5-disc box set entitled Hard Road: The Mark I Studio Recordings, released tomorrow (July 28) via PLG.

Simper, 69, tells TeamRock: "It was a very exciting time – the band was brand-new and we were thrust together to make the first album in 18 hours. I think we did a pretty good job.

"It's quite amazing that we recorded almost all live, and with only four tracks. I had to share a track with the drums. That put a lot of pressure on us; when that red light went on, none of us wanted to be the guy to mess it up.

"I think that energy comes through. People say there's something magical about 60s records and I'm sure that's what it is – the adrenaline that came with recording that way, with no room for error, just being musicians in a studio together. That nervous tension definitely transferred to the vinyl."

Looking back, Simper knows why the band were pushed to work so hard. "Our US management wanted to grab the big dollar while it was available," he says. "Three albums in little over a year would never happen today. Once the money started to slow down we were just discarded. We worked and worked and worked – then we were treated as disposable pop artists. The Mark II version of the band never had that pressure."

The bassist will never forget the "frantic" months between Purple's first show in Denmark in April 1968 and his final appearance with them in Cardiff in July 1969, plus the studio works created in between. And although he was fired when Gillan insisted on bringing Glover on board, he's still proud of what his lineup achieved with limited resources.

"I guess it's almost heritage stuff now," he says. "Nobody would have thought that nearly half a century later there would be any interest in it. These reissues and box sets are like musical antiques and it's lovely that people want to explore them."

Simper believes Purple set the tone for a change from the three-minute pop songs of the era to a "more expressive, indulgent" style of rock: "We felt we spearheaded something – longer songs with more musicianship."

Hard Road: The Mark I Studio Recordings is available for pre-order now.