As Belle & Sebastian prepare for some summer dates, it's 20 years since the release of Tigermilk and If You're Feeling Sinister. Malcolm Jack gets his thinking cap on to analyse the scientific elements which make up these groundbreaking albums.

Tigermilk

25% – on the rock'n'roll Oddly we can probably thank the government for Belle & Sebastian. Founder members Stuart Murdoch and Stuart David met on a training-for-work course for unemployed musicians in Glasgow which they were attending partly to earn an extra tenner of dole money. Murdoch spent the time honing some songs he'd written, which they eventually got to demo, Tigermilk's majestic soon-to-be opener 'The State I Am In' included. The die was cast.

25% – we formed a band Tigermilk was recorded and mixed at Glasgow's CaVa studios in just five days in March 1996 and released three months later. A remarkable feat by any measure, but especially when you consider that the fledgling band's members had all only recently met: Murdoch and David recruited guitarist Stevie Jackson via an open mic night at The Halt Bar; drummer Richard Colburn was David's flatmate; cellist / vocalist Isobel Campbell, keyboardist Chris Geddes and trumpeter Mick Cooke were found through friends. For a bunch of relative rookies their playing is remarkable, wrapping Murdoch's poetic Dylanesque strums in warm baroque-pop à la The Left Banke.

30% – 'do something pretty while you can, don't fall asleep' From 'Expectations' to the gorgeous 'We Rule the School' – from which the above lyric derives – youth fantasies are a recurring theme on Tigermilk and most subsequent B&S records. Murdoch has chronic fatigue syndrome and spent parts of his late teens and early 20s barely able to get out of bed. His songs come from a place where everyday events and experiences of a boy's formative years take on a near mythical significance.

15% – whimsical girls From the titular ditz whose first cup of coffee tastes like dishwater in 'She's Losing It' to 'Mary Jo', who only wants 'a cigarette and a thespian with a caravanette in Hull', women with more than a whiff of whimsy about them populate the album like characters from some kind of kitchen-sink comic book.

15% – taped off the radio It's a nerdy footnote to the making of Tigermilk, but the story of track five says much about the record's naïve magic. A bip-bopping trippy Casiotone jam inspired by New Order's 'Procession' and something of a sonic oddity on the album, 'Electronic Renaissance' got its first advance play on BBC Radio Scotland's Beat Patrol. Murdoch recorded the broadcast to cassette and loved the tinny, compressed sound so much that this crudely captured second-hand version became the one used on the final album.

If You're Feeling Sinister

40% – on a rock'n'roll Released less than half a year after Tigermilk, Belle & Sebastian's arguably career-defining second is the sound of a band on a roll. Its personnel and sonic palette are substantially the same as its predecessor, but there's an assertiveness in the playing that speaks of a group rapidly coming into their own, from Jackson's variously jangling and thrumming guitar on 'Me and the Major' and 'Mayfly' to Cooke's rousing trumpet fanfares on 'Stars of Track and Field' and 'Judy and the Dream of Horses'.

25% – fans only Where Tigermilk initially received a limited release of just 1000 copies, few of which ever left Glasgow, If You're Feeling Sinister was the first Belle & Sebastian album to be properly distributed and bring the band to a wider audience. And yet the group didn't exactly play the industry game. They rarely did interviews nor posed for photos, and their live appearances remained fleeting. An intrigue grew about these mysterious Glaswegians that captured imaginations on both sides of the Atlantic.

20% – definitely not Oasis Picture the musical landscape in November 1996. The Prodigy's 'Breathe' was the number one single and Robson & Jerome were dominant in the albums. Earlier that summer Oasis played for half a million people at Knebworth and Britpop was in peak swagger. What a breath of fresh air this album and band sounded to ears in search of something gentler, stranger, funnier, more literate and playful.

10% – even more whimsical girls On the title track, Hilary is 'into S&M and bible studies, not everyone's cup of tea', while the album's closer 'Judy and the Dream of Horses' pertains to a teenage rebel who 'did it with a boy when she was young' and dreams about stealing horses. There can barely have been an oddball femme knocking about 1996 Glasgow who somehow didn't get a mention in a Belle & Sebastian song.

15% – godliness / ungodliness The album's title track and centerpiece is a beguiling juxtaposition of religion, teen suicide and self-interference concluding with the memorable lyric: 'go off and see a minister, chances are you'll probably feel better if you stayed and played with yourself'. With considerations of faith, sex and romance swirling around his head, a wry sense of humour and a keen knowledge of the classic pop pantheon, nobody else was writing songs like Murdoch back then. Twenty years on they still sound divine.

Belle & Sebastian play Glasgow University Union Debating Chamber, Mon 13–Wed 15 Jun