THE biggest challenge when it comes to recreating the distinctive sound of the Californian rock band, the Eagles? That, says Jim Bowie, would be their pristine harmonies. “We’ve found that you need at least four people in our band who can sing,” he says. “Working on the music itself, getting the foundation, is one thing, but the harmonies are obviously the main thing. But it’s also the biggest reward, because when you’re singing harmony, there’s just something about it when it all locks together. The harmonies are like another instrument. It’s great when it comes off, but when you don’t get it right, it’s like listening to a child learning the violin.

Bowie, 52, is part of the Eagles tribute band, Hotel California, which celebrates its 20th anniversary next year. They have taken the songs - Take It Easy, Witchy Woman, Life in the Fast Lane, Desperado, and, of course, Hotel California - all over the country, including the SECC and the Usher Hall. They’ve played in Melbourne and India and have even supported former Eagles guitarist Don Felder a couple of times when he appeared at the Dunhill Cup at St Andrews

From the Rolling Stones and Pink Floyd to Elvis, AC/DC, the Beatles, Rod Stewart, Beyonce, Oasis and Taylor Swift, many major-league pop or rock acts have their dedicated tribute acts. As once noted, they've become a subculture all their own: “What started off years ago as a way for some friends to get together and celebrate the music of their favorite bands by playing their music has become an important, and lucrative, part of the rock landscape, with many up-and-coming musicians cutting their teeth in tribute bands before launching their own careers.”

"There's a tribute band now for almost every act, it's incredible," says Neil Drover, whose agency provides music, entertainment and event management. "There are some fabulous ones, like Hotel California and Chic Le Freak. The popular bands for tribute acts and audiences are still people like Abba, Take That, Robbie Williams, Rod Stewart. But there are also a lot of acts like The Soul Kings and Men of Motown, who do songs from a particular era. They're all very popular."

Unfortunately, observes Jim Bowie, “there’s a bit of a stigma about the phrase, ‘tribute’. I think it stems from acts trying not just to sound like but also look like the band they’re trying to emulate. It has given itself a niche and a bit of difficulty in trying to progress itself anywhere. Other than the big boys, like the Bootleg Beatles and some of the big Queen and Abba acts, the whole tribute scene is a bit of an odd one, if people foresee that acts are dressing up as well as trying to play the music. We’ve spent the last 20 years trying not to look like the Eagles. They were pretty nondescript anyway: jeans and T-shirts boys. We’ve never had to worry too much about trying to look like them, we just concentrate on putting on an entertaining show in a theatre environment and doing the best with the music.”

Hotel California was formed by two guitarists (no longer part of the line-up) who wanted to replicate the twin-guitar solo in the Eagles' classic of the same name. The solo, one of the best-known in rock music, was played by Don Felder and Joe Walsh; no wonder Bowie speaks with pleasure of the times he played it with Felder. “It’s a great honour to meet your heroes, and it was a great honour for me to share the stage and play that solo with him. These experiences are all part of the musical family that has been created around the whole thing. We do this for the experience. We’re all in full-time employment, pretty much, so this is a hobby for us. We want to keep it fresh and fun, and we want to have life experiences on the back of it. We were in India a couple of years ago. We’ve played Italy and Australia as well.”

Hotel California’s next date is in Rutherglen town hall on April 7 but the band has another tribute project, playing the music of two classic English rock groups, Free and Bad Company, with dates in March and October. “We don’t try to look like Paul Kossoff or Paul Rodgers,” says Bowie. “We do our best with the music and make it entertaining.”

Blondie, another best-selling 1970s American band is honoured by Dirty Harry, formed in Edinburgh in 2011. Dr Sarah Kennedy, a psychiatrist, channels the singer, Debbie Harry, rather well. She was in a Mod/soul band when she had the idea of a Blondie tribute act. “I thought the idea had potential because I’d looked online and there weren’t really many good Blondie tribute bands. If there were, they were only doing the very bare essential songs - there was nothing really very authentic.”

Dirty Harry was formed quickly after she put an ad on Gumtree. “We all just instantly got on. As musicians they were very tight, so things came together so I got the luxury of perfecting the vocals and the performance. Things just went from strength to strength. I never thought I would enjoy being in a non-originals band as much but we have quite a following now. It doesn’t actually feel like a tribute or a covers band; it feels like a band in its own right.

“Vocally, you’ve also got to pick a tribute act that you think you could pull off. “ She laughs. “There’s no point in me trying to do Aretha Franklin. And there seemed to be a gap in the music scene for that. Most bands are male-fronted. Unfortunately, a lot of female musicians fall out of live gigging in their late twenties.”

The tribute scene is a crowded one, then, but Dirty Harry stand out partly because the original music keeps being rediscovered by younger people. Not too many tribute acts are fronted by a woman playing a larger-than-life singer into the bargain. “And there are no Blondie tributes that I know of that do the full back-catalogue of songs and can also try to recreate that vibe. There’s still a very active passion and following for Blondie, even though the band is 40 years old." The audiences include “children of people who’ve been into music in general, not necessarily Blondie. I’m always amazed that there are early-twenty-something kids who turn up and know the words to quite a lot of the songs. There’s a coolness now about being into nostalgic music. The other thing to stand out is, you have got to have some degree of loyalty and put the leg-work in in the early years in getting your following. We’ve got a lot of loyal fans who will spread the word and support us and are interested in what we’re doing.

“We’ve been on the circuit and played with a lot of different tribute bands and the best of them try to tribute the original artists. We’ve met some tribute bands and I think the only reason they got together is because the front person or whoever has put the band together wants to feel like they’re the original artist.” But there was no such narcissism with Dirty Harry - “I was always very keen that we try and do as best a job to the original as much as it can be, rather than it being all about us as individual musicians.”

It can, though, be expensive to dress as Debbie, even if she did tend to dress in thrift or hand-made clothes. The money that Dr Kennedy makes from the band is “put back into costumes, because part of the routine of getting into character and the role is that you have the confidence and also the ability to hide behind the mask of being somebody else.” Dirty Harry’s next gig is at Glasgow’s Oran Mor on April 21.

Sound advice for tribute bands hoping to make it big comes from Iain Gordon, who as manager of Glasgow’s Pavilion Theatre has put on many tribute acts and touring production shows. “For me, the tribute acts that do well are tributes to people who are dead and the ones that put a bit of effort into it. The trouble is that there’s an awful lot of tribute acts that do clubs or pubs and think they’re doing well, then they’ll do a theatre. But they’ll do it with nothing. You say to them, you need production when it comes to theatre; you need video, good sound, good lighting. And half of them don’t appear like that. So there’s a big difference between a tribute act in a pub or club and a successful tribute act in a theatre. A lot of them don’t make that crossover.”

He singles out Talon as a great Eagles tribute band and backs up Jim Bowie’s point about having more than one singer in order to handle the Eagles’ trademark gorgeous harmonies. “The Talon guys change over to different instruments on stage and do the vocals on different numbers - they’re like the Eagles in that respect,” he says. He also likes T-Rextasy: “We’ve been doing that for 14 years now and they still do 1,100 people every time they appear at the Pavilion.”

Gordon has cut back on the number of tribute bands he stages, partly because there are so many of them, but he looks out for acts who pay tribute to original bands that fans might not see again. “So I wonder, will the Stones or the Eagles ever tour again? So it’s okay to put these acts on. But I think the market is for acts that are dead, where people know they will never see them again.”

At one time, incidentally, it seemed like the Eagles would never tour again, after the tragic loss of co-founder Glenn Frey. That would have left the field open for bands such as Hotel California and Talon. But you can never keep a good seventies rock band down: Don Henley & co are back on the road again, in North America.