THERE are things which are not meant to be understood by man. The time-space continuum. Why you never see baby pigeons. The original sleeve notes to Blood On The Tracks. That Nike football advert with Edgar Davids and the bloody robots. Why grown people find Victoria Wood funny. And to this little list can be added ''Why Michael Marra isn't famous''.

Marra must be sick of reading reviews of himself which compare him either to Randy Newman, Loudon Wainwright III, or Tom Waits, suggesting a weird composite: one-part curmudgeon with a grim Dundonian croak of a delivery and one-part wag with upturned hat-brim, relentlessly spouting gags. Marra is, of course, neither. He is simply the Greatest Living Scotsman. Why then, is he finding such difficulty finding a taker for his brilliant new album, Posted Sober?

''I'm shopping around,'' says Marra drolly, but neither his most recent label, Eclectic, nor the Dundee-based Mink he has worked with in the past, seem likely outlets for a 15-song collection which will be greedily devoured by fans. In the meantime, the best way to hear this splendid batch of new works is at Cottier's in Glasgow's groovy West End next Tuesday. Some might also surface tomorrow on Janice Forsyth's Radio Scotland show.

The new album, whenever it does surface, is a radical departure. None of his familiar piano, for one thing, 36 real musicians for another. ''I was never dedicated to being a pianist,'' he says. ''I don't like my playing. My technique is flawed, so there's hardly any on this album.

''It's a bit ironic this album is taking so long to come out as we took a great deal of trouble over the engineering of it. Every other record I've made has been compromised in some way. I suppose it would be different if I sold large quantities of records. But with each one I have to battle and fight and scrape and steal to get it made at all.''

It's worth it, though. The elegiac Lonesome Death of Francis Clark and hilarious Angela Gunn (''don't wipe yer nose with the back of your hand/Use yer sleeve like a civilised man'') are instant additions to the surely imminent The Best Michael Marra Compilation . . . Ever collection, while others showcase the familiar Marra lyrical trick of placing the incongruous in familiar environments.

But, as ever - and best of all - while Scotland again seems to be full of dimwits singing as though they come from Nashville and Los Angeles, Marra still sounds gloriously, full-strength Scottish.

Which presents its own dilemmas. Recent dates in California and Italy have tested the locals' aptitude for the Lochee patois. He grins: ''I was invited over to Mendocino in California and when you're there, with songs like Baps'n'Paste, yes, I do have to furnish a glossary. But I played a date in a place called Healdsburg, where Tom Waits lives. He didn't come to see me, but I bought The Mule Variations there.

''In Turin I told the audience that as a bairn I'd met Gianni Rivera, of AC Milan, in the street. They were in Dundee to play in the semi-final of the 1963 European Cup. They looked like film stars. When I said it on stage this guy in the front row stood up and turned to the audience and began counting backwards through the years, obviously ratifying what I'd said. When he finished and was satisfied it was true, there was a big roar of approval.''

Owing to the curious process by which Posted Sober was born, there will be as many out-takes as tracks included. Marra recorded 30 songs then passed responsibility for song selection to producers Allan McGlone and his brother Christopher. ''It was a big departure,'' he says. ''But sometimes you get too close to songs and I was interested to see what they did. There was one song they didn't pick, called House Room, which I was tempted to make a case for. It's set in the recent conflict in Eastern Europe and it's about running through a neighbour's house to get a library book. Maybe I'll get somebody else to record it.''

Other people's interpretations of his work have paid the bills. Marra is perhaps doomed to be remembered for one song - the anthematic Mother Glasgow, best-known for its recording by Hue & Cry, even though an equal amount of coverage has been given to Hermless, a hymn of devotion to a naif. But he is far more idiosyncratic and individualistic than those songs imply. A relatively slender body of recorded work (five albums in 20 years) only hints at his greatness: 1980's The Midas Touch'' (unfindable but perfectly-all-right-in-its-own-way) was followed by the mighty Gaels Blue, which contains the mind-boggling, heart-breaking Happed In Mist.

On Stolen Stationery followed, but 1993's Candy Philosophy is the place to start, containing his marvellously surreal King Kong's Visit To Glasgow, the beautiful, tragic Australia Instead Of The Stars, and a lively tribute to the French Elvis, Johnny Halliday. A live album, Pax Vobiscum, containing a hilarious account of marital wreckage, Beefheart & Bones, as well as his wry barb at religious nuttiness, Chain Up The Swings, brings us up to date.

But a ton of stuff remains unrecorded: This Plough, a lovely song about former Russian premier Mikhail Gorbachev's mother (!), his stunning rip through Robert Burns's Green Grow The Rashes, the hilarious Dundonian housing scheme eulogy Baps'n'Paste, and Mack Rebbenack's Visit To Blairgowrie, about - yes, it did happen - the Night Tripper's trip to rural Perthshire.

Fortunate is the man who can be so cavalier about discarding work of that quality. Make this man a star and you're making the world a better place.