"Is there a D# missing?" he asks.

"There's a D# in the recording," says Rebecca Bottone, a young soprano with big eyes, big lungs and short, chic Jean Seberg hair. "I think it's quite sexy, the D#."

It's a little after lunchtime in a rehearsal room on Elmbank Crescent in Glasgow. I'm here because Glasgow has been named a Unesco City of Music in acknowledgement of its musical heritage (no, not Sydney Devine, he's fae Ayr) and ongoing status as a town which rings with tunes.

My mission is to hear as much music as possible by walking round the city in a random sort of way. It's a sonic daunder.

Go anywhere in Glasgow and you'll hear music coming from cars, bars, shops and streets. In July, you may hear the flute and drums more than is pleasant, but for the most part, citizens accept that noise pollution is a fact of life. It's the Glaswegian equivalent of file-sharing.

An average of 127 musical events are staged each week in Glasgow. But that's concerts you pay to get into. There are loads more impromptu gigs, and, of course, bags of buskers. Halfway down Buchanan Street, Jim Ward, 53, is sitting on his amp, and wringing from his Fender Strat the twangiest notes this side of Duane Eddy. He plays in a band, The Magic Blues Surfers, but busks as a way of earning during the day. He has 90 minutes of material, but waits till lunchtime to break out the big moneyspinner – 'Apache' by The Shadows.

"The hardest thing about this for me," he says, "is bagpipe players and drummers. I'll be playing and they set up 20 yards away. It totally drowns me out."

At the junction of Argyle and Miller Street, I stumble across the sort of act he has in mind, surrounded by a crowd of about 100 people filming them on their mobile phones. Clanadonia (slogan: "Keepin' It Tribal") are four drummers and a piper, mostly dressed in kilts and leather waistcoats, a grungey, beardy 'Highlander' meets Kurt Cobain look. The exception is the piper, Brad, a new recruit whose crewcut and vest are more Vietnam than Culloden. "Aye, a couple of months ago he was in the shortbread-tin gear and playing on Buchanan Street himself," says Robbie, one of the drummers. "It's kind of like 'Charlie's Angels'. We found him, we took him away from all that, and now he works for us."

Clanadonia started as stuntmen, working on films including Braveheart and Gladiator, and the music developed from entertaining the crew between scenes. They don't do much stunt-work now – "We're tired of getting our heads kicked in for a living." They travel the world as musicians, playing to the Tartan Army in Paris when Scotland gubbed the French.

A brisk walk east brings me to St Andrew's In The Square, a fantastic old church. It's home, every Thursday night, to the Star Folk Club, which this year celebrates its 30th anniversary. Different acts perform each week, playing in front of the pulpit, the high ceiling shining with golden cherubs and thistles.

It's a long way from the club's first premises, the Communist HQ in Calton Place, but there's still something of that in the air. Tonight's opening act, Ian Davison, one of the most venerable figures on the folk scene, introduces his opening song thus: "This one's called 'Here's To John McLean'. I wrote it in 1973." Davison is accompanied by a young woman called Carissa Bovill, a student at RSAMD, who plays the piano and sings 'Ae Fond Kiss'. She has a beautiful voice, and the whole thing is made more resonant because this is the very church in which Agnes McLehose, for whom Burns wrote the song, was married.

The headliners are Sinsheen, traditional singers Barbara Dimmock, from Dundee, and Christine Kidd, who, like the famous gingerbread, hails from Kirriemuir. You've got to love an act who have a song with the opening line: "On Friday, I have a bridie."

It's getting on for 11pm and, acting on a tip from Alex Kapranos, I leave for the west end to meet Isosceles, a band much fancied as the next big thing out of Glasgow. It's a measure of the buzz around them that they have been chosen to play in the Scottish pavilion during the forthcoming Venice Bienalle. A four-piece in their mid-twenties, they are based in the Studio Warehouse, a former Customs and Excise building by the Clyde, near the Tall Ship.

Walking down the lane in the rain and dark, past railway arches, is frightening – all shadows and David Lynchy industrial clank and wheeze – but worth it. The Warehouse is an amazing space – cavernous, grafittied, filled with music. Loads of artists work here; someone is growing tobacco plants on the top floor. There's a photo studio in which, recently, models auditioned for a Wonderbra campaign. "Everyone made sure they came in to pay their rent that day," laughs Jack Valentine, singer and guitarist in Isosceles.

He shows me into their space, a small ramshackle room full of character and kit. "We usually arrive about this time of night," says Valentine, who has the youthful good looks of a doomed war poet. "Our room isn't sound-proofed. The girls doing screen-printing are directly above us. When we're practising a tune, trying to get ready for a gig, it drives them nuts because they're hearing it 40 times. It's better to work when everyone has left. You can be as loud as you like and totally focus."

They play a four-song set, reminiscent of Orange Juice and Television, which brings my day of music to a rather brilliant end. It's midnight, and Glasgow's choir of drunks is out in force, but it's time for me to give my ears a rest.