As commercial radio in Scotland gears up for its 40th anniversary, market leader Bauer this week unveiled a makeover of its heritage stations as it grapples with the digital age.

As the 1973 pioneer Radio Clyde, the FM station Clyde 1 has grown its listening hours by 34% in a year, while Forth 1's hours are at a 10-year high, helping Bauer to a 13% listening increase and a 22% market share in the central belt.

But this week listeners to the company's five AM stations – Clyde 2, Forth 2, Northsound 2, Tay AM and Ayr-based West Sound – woke up to the same breakfast show for the first time, part of a more unified branding of its Greatest Hits Network (GHN) of legacy stations, which account for 15% of Bauer Scotland's total audience and 10% of revenues.

Two new weekend shows, including one on Scottish politics, will also begin across the GHN stations today.

Bauer Scotland has in recent years wrested market leadership back from rival Real Radio and under managing director Graham Bryce now has 50% more audience than nearest rival Radio 2.

Mr Bryce said the next challenges were the mobile multimedia lifestyles of the 15-24s and the eventual analogue switch-off.

He said: "Every media company is facing these challenges, but radio is interesting as so far we have been less affected by the changing world and digital environment. But it's coming upon us as well, we are going through the same process TV did."

Half of radio listeners have already gone digital, and the Government is set to decide by the end of the year on whether and when to switch off analogue and kill AM radio – Bauer acquired 41 UK analogue licences with its takeover of Emap five years ago.

Mr Bryce says the impending switchover, though many years away, gives an opportunity for these stations to reinvent themselves and appeal to a wider market. He said: "Radio 2 five years ago was seen as old, dusty, for my gran, and it went through a revitalisation – we are going through that same process."

While UK radio giant Global networks its flagships such as Capital, Classic FM and Heart nationwide, number two Bauer has stuck with local identities and content.

Mr Bryce says: "Our belief and experience is that it engages the listeners more than a station broadcast from London or Manchester or somewhere else."

He says research has shown local station listeners are more receptive to advertising in a tough environment, and while television has seen its audience fragmented, radio's consumption base has proved remarkably resilient with 90% of people in the UK still tuning in.

However, Mr Bryce says radio has somehow to keep the attention of the key 15 to 24 group when it "hasn't necessarily got the shiny new buttons of some media".

Already almost 40% of the younger radio audience listens via mobile phone, so regularly updated apps are essential along with a potential move into i-Player- style' time-shifted' listening.

However, the radio boss says he does not feel challenged by the likes of web firm Spotify, which has 10 million listening hours against radio's one billion.

He said: "They like to call themselves radio but in our view they are not a direct competitor to what we do... the curated environment with live presenters."

Mr Bryce says the AM makeover reflects a hybrid model and Bauer Scotland, which employs some 350 staff and presenters, is increasingly operating as a unified business but will protect radio heritage. He said: "It has a unique place in the hearts and minds of listeners. Clyde is as strong today as ever, and not many media can say that after 40 years."