By Pauline McLean BBC Scotland Arts Correspondent

Bill Wyman is among the leading acts at next year's event

There seemed little to offer between the excesses of Hogmanay and Burns Night, and little point in staging anything in between.

All that changed when a box office clerk at the Glasgow Royal Concert Hall decided what everyone needed in the depths of winter was another festival, this time devoted to music.

Celtic music to be precise - and with Dougie McLean, Altan, The Chieftains and the Battlefield Band, there was no quibbling about the music matching the description.

Today, it's a different matter.

Celtic Connections is now one of the largest winter music festivals in Europe - and one of the most recognised Celtic music festivals anywhere in the world.

Its definition of Celtic has expanded too.

Americana, indie and world music are all fair prey. Steve Earle isn't an obvious Celt - but with his roots in American country music, there's definitely a connection.

African music legend Baaba Maal will be worth seeing in his own right, but how much more in collaboration with some of our finest folk musicians?

Ditto KD Lang, although she's Canadian, so she's bound to have a Scottish granny and with a name like Lang, she won't be buying her own drinks in the festival club.

World music isn't an obvious connection, either, unless you consider the parts of the world like Brittany, Catalonia and Nova Scotia, where Celts have settled.

But by bringing together groups like Italy's Mondine di Nova choir and the Bulgarian Voices Angelite, with card carrying Celts, you're guaranteed some sort of connection, however tenuous that is.

The roll call of established Celtic names - Karine Polwart, Sharon Shannon, Luka Bloom, Mike Scott and Julie Fowlis, Shooglenifty, Capercaillie, Moving Hearts - is impressive in its own right but it's the potential for collaboration which gives this festival the edge.

African music legend Baaba Maal will be worth seeing in his own right, but how much more in collaboration with some of our finest folk musicians?

Where the festival goes wrong is when it's too po-faced.

Surely Canadian KD Lang has some Scottish ancestry

Some of the opening concerts have been a bit too radical in their selection process - one so radical it didn't happen at all.

Where it works is in natural collaboration, not least at the last night jamming sessions in the festival club.

How else to celebrate its 15th anniversary but with a huge jamming session featuring some of the finest Celtic performers of the moment?

But there's humour too in two concerts entitled Harp Heaven and Accordion Hell - based on a Gary Larson cartoon from the Far Side.

All in all, it's an impressive line-up, with some interesting collaborations.

Is it entirely Celtic?

Perhaps not enough to convince the purists - but there's enough to persuade you out on a cold January night in Glasgow.