With the violin and cello packed side by side in the back of the car, we’re on the road home from our gig in Dundee. Cellist Su-a Lee is reminiscing about the first ever Mr McFalls Chamber gig, 20 years ago, at a notorious nightclub called the Transporter Rooms.

“It was really late. 2am probably. We were on stage playing Webern, and there was a man dancing to it! That was when I thought, 'We’ve made it, this is where it’s at'”

As I wonder what that Webern dance might have looked like, Su-a describes how they had arrived at the club quite late that night.

"It was about 10pm, and it was still too early for the club world of course. Don’t tell anyone, but we got absolutely hammered. I remember Brian [the group’s viola-player] was quite worried when he discovered I had been drinking gins and tonic before going on stage. And he didn’t know they were doubles.”

Now of course, I’m wondering what on earth that Webern might have sounded like too.

And from this inauspicious beginning in the dark club-rooms of mid-nineties Edinburgh, the McFalls string quintet leapt with glee into the gap between standard classical repertoire and "popular music" idioms.

"The early days were totally wild," Su-a admits, "but they affected me deeply as a musician. Playing and expressing music in a completely different way to how I had been trained – I wholeheartedly embraced it, and I would say it made me a better and more rounded musician."

Stories of the early days include tales of bathtubs on stage, players adopting permanent stage aliases and some bold fancy dress. But although the heady days of experimental avant-garde performance style may be a thing of the group’s legendary past, Robert McFall’s penchant for free-ranging and eclectic programming has remained a cornerstone of the group’s identity.

As a typical example, the programme that Su-a and I have performed this week, called Island Life, weaves a thread of connections between Caribbean island music and Scottish island music, via the dark story of the Scottish slave trade. There’s a bit of Purcell, some Kurt Weill, Cuban composers and Robert Burns, with a brand new commission from composer Erollyn Wallen thrown in for good measure.

In an age that has abandoned the album format for streaming tracks, such varied listening selections might now be considered a norm. But where else do you go, other than to Mr McFalls Chamber, to hear live musicians perform such wide-ranging programmes as this group do?

The most surprising programme I ever performed with the group was called Freak Out. It featured the music of 1960’s rock legends Captain Beefheart and Frank Zappa, arranged for strings, keyboard, percussion and French horn (played by Scottish Chamber Orchestra principal Alec Frank Gemmill), with some George Crumb, just to keep everyone on their toes. It was an unholy, wonderful, astonishing noise, and enormous fun.

Asked to comment on their influence, Su-a describes how "McFalls had a huge impact on the musical scene in Scotland. There was definitely nobody close to doing what we were doing here - not for years."

She is referring not just to the programming, but also to the group’s well-known enthusiasm for adventuring into new musical territories. Their many and varied collaborations with artists from other musical genres have earned the group a special place in the hearts of many musicians across Scotland, from all backgrounds, and left a rich legacy of recordings.

Featuring in the Island Life programme is Susan Hamilton, soprano. A longstanding collaborator with McFalls, Hamilton is predominantly a baroque specialist who loves working with McFalls, "because its a wonderful place to create and work together with other musicians."

"It is," she says, "a liberating, respectful and glorious musical experience."

For audiences too, Hamilton claims that McFalls can be a "life changing experience", with loyal listeners often finding themselves "hooked" by the group. When on stage, making music with musicians from all backgrounds, Hamilton describes the feeling that "the audience come with you, as you take musical risks together."

Getting Robert McFall himself to take any credit for all (or even any) of this is very hard to do. For two decades, Robert’s arrangements for the group have arguably been the best-kept secret of the group’s success. His arrangements are, says Su-a, are "second to none – no question about it. The wilder the challenge, the more brilliant his arrangements."

In all the projects I’ve played with the group, I’ve never seen Robert’s name actually appear on a single arrangement, programme or printed part, and to raise the subject of copyright with him is to earn a stern look. But you can only hide your candle under a bushel for so long, and the music scene in Scotland seems to have decided 20 years is long enough. Shining a light on this talent at last, Hands Up for Trad has just awarded Mr McFall their 2015 Ignition Award. Furthermore, and most excitingly for future musicians, his outstanding arrangements are soon to be made available online, as a free resource.

True to their mantra of making the musically impossible a reality, Mr McFalls Chamber are currently touring no fewer than 4 different programmes at once. Their official 20th birthday celebration, at the Queens Hall in Edinburgh on Monday October 12, will showcase their Baltic music programme, Solitudes, and mark the launch of their new CD of the same name. Go and see them. But be warned, it might just change your life.

Mr McFalls Chamber's new Baltic Reflections programme is at Tolbooth, Stirling on Sunday and Queen's Hall, Edinburgh on Monday. The new album, Solitudes, is out now on Delphian.

www.mcfalls.co.uk