IT'S often said that the strength of Scottish actors comes from the sheer range of work they're asked to do. If it's December, they'll be singing and dancing through a raucous pantomime. Early spring, they'll be free-associating in an experimental multimedia showcase. By the summer, they'll be acting their socks off in some weighty classic for a global audience at the Edinburgh Festival. Come autumn, they'll be touring a broad Scottish farce, with a quick Taggart squeezed in to pay the bills. Only the multi-skilled need apply.

Yet when Jennifer Black turned up in a vampish wig, belting out number after wordy number in Forbes Masson's comedy musical Stiff! at Edinburgh's Royal Lyceum, many people were surprised. ''A friend of mine came to see the opening night and said he didn't even know I could sing,'' says Black. ''He associated me with being a serious actress. I don't put any limitations on myself, and sometimes it's quite a shock when people say how they perceive you.''

Of course she can do it, but it's a talent you'd have overlooked unless your memory stretches back to her parts in Wildcat's Musical Chairs, or Borderline's Guys and Dolls. The voice is just another string to a bow that has been put to exceptionally good use in the past few months. In a profession beset by unemployment, Black has landed an enviable chain of plum jobs since last summer when she starred in David Harrower's Kill the Old, Torture their Young, one of the Traverse Theatre's high-profile contributions to the Edinburgh Fringe.

From there, she changed roles, mounting a revival of Therese Raquin, the Zola adaptation she directed for Communicado at the Royal Lyceum. Then she was back at the Traverse playing an abused daughter taking her revenge on her elderly father in Linda McLean's One Good Beating. Meanwhile, she was rehearsing at the Royal Lyceum for the mammoth lead role in Iain Heggie's back-green comedy An Experienced Woman Gives Advice - she was that experienced woman. And while she was performing that, she somehow found the energy to rehearse the lead female role in Stiff! Who cares if she doesn't know what she's doing once the seven-week tour comes to an end, tightened and edited since its Edinburgh debut - she deserves the rest.

''Energy begets energy,'' she says. ''The energy you can build up from doing lots of things helps. I didn't feel that I was spreading myself too thin, quite the reverse. But then I just love working.''

One particular blessing of her recent run of work has been the rare chance to play not just romantic but downright sexy leads, breaking the taboo that forbids such licentious behaviour for women over the age of 30, let alone 40. It's a trend that has also been enjoyed by her friend Siobhan Redmond, with whom she starred in the Tron Theatre's magnificent 1995 version of The Trick is to Keep Breathing. It was Redmond, in fact, who had the first shot at An Experienced Woman Gives Advice when it played in Manchester three years ago, playing Bella, a teacher in her late thirties with a boyfriend barely over 20.

''An Experienced Woman was a brilliant part, and Stiff! too - all credit to Forbes Masson and Caroline Hall, the director, that they didn't go out and get a 25-year-old,'' says Black. ''I don't have a problem with getting older. The problem I have is other people's problem with women getting older. How many times have you heard somebody looking at an older actress they haven't seen for some time and saying: 'Oh God, she was so pretty when she was young!'? That's terrible. You don't do the same thing with men. Men develop character in their faces, women just develop wrinkles.''

Where Redmond tackled Heggie's heroine with flamboyance and dazzle, Black's approach was deadpan and understated. It was a selfless technique that worked to the comedy's advantage, never forcing the jokes, but letting them emerge naturally, rooting the character in a recognisable predicament. ''I know Siobhan so well that when I started to read the lines, I had her voice in my head,'' she says. ''Even though we're close friends, our acting styles are totally different. So after a few days of doing the Heggie piece, I just had to get rid of that idea and do it my own way.''

She uses much the same unshowy comedic gift in Stiff!, in which she plays first the prim girlfriend of Forbes Masson's monumental sculptor, George Mathieson, then the devilish gangster's moll who tempts him off the straight and narrow. As the spurned girlfriend, she qualifies for two of the musical's best songs: Die Soon and Nun (With One Lung). Profane and irreligious as they are, these numbers surely confirmed to the Royal Lyceum's regular audience, among them many language police, that Black's name is synonymous with vulgarity. Some would recall the near-the-knuckle comedy of 1997's Dead Funny, others were still smarting from all the c-words in An Experienced Woman, and here she was singing about someone's testicles getting snagged on a rusty nail.

''In Stiff!, I really have to think hard about what it is people

are being offended by - which makes me sound totally unshockable, but I'm not,'' she insists. ''Maybe I'm just shocked by different things. I'm shocked by cruelty and by violence, I'm not shocked by bad language.''

So what about the line she sings in Die Soon, a litany of malevolent wishes, about having her ex-lover anally impaled on a railing? ''I think that's funny,'' she says, laughing out loud. ''What does that say about me? With all of those lyrics, I marvel at Forbes's dexterity rather than being offended. Someone told me that every woman should learn the lyrics to Die Soon, because every woman at some point has felt that about some man. And probably some men about some women . . . No?'' Well, that's another story.

n Stiff!, King's Theatre, Glasgow, today to Saturday.