First River Phoenix and Keanu Reeves, now Johnny Depp wants to be a rock god. Why isn't being a film star enough? Ryan Gilbey reports
It's the same reaction you'd have if your child reached for a hot stove. Hearing that Johnny Depp and his band P has been signed (for £500,000) by Capitol Records, you want to cry: "For goodness sake, Johnny, get away from that damn guitar before you hurt yourself!" Squandered dough, punctured egos, jobless A&R men, EC CD mountains - when actor meets recording contract, the results can be catastrophic. You'd need an almighty Band Aid to patch up the damage.

Acting genius never translates into musical prowess. Anyone who heard the dire, sub-folk contribution that the late River Phoenix made to the animal rights album Tame Yourself can testify to that.

His enthusiasm was exceeded only by his pretentiousness. Here he is on popular music: "I liked the Smiths, before they got self-indulgent." And this from a man who wrote a song called "Aleka Dozy Encircles".

And here he is revealing the story behind the name of his band, Aleka's Attic: "Aleka is a poet philosopher. The attic is a meeting place where he has a secret society. They come and visit him and read his works. He then dies and (they) continue the readings of his works, and from that learn ... new passion for life. And they express it through music and form a band." Couldn't they just have consigned their passion to a wad of A4 in a bottom drawer like the rest of us?

What could have persuaded Phoenix to pursue a professional career in music? Clearly his motivation was neither money, nor recognition per se: Hard Rock Caf waiters the world over dream of the kind of acting success he achieved.

But despite being besieged by worshipping fans, he remained one crucial step behind his friends Michael Stipe, the Butthole Surfers' Gibby Haynes and Red Hot Chilli Peppers' bassist Flea, in the search for artistic credibility. Every teenager wants to be a rock star. If you had a record player, a full-length mirror and parents who popped out on a Saturday afternoon, you'll remember the fizz in your head from miming to whichever 7-inch you'd nicked from the Woolworth's bargain bin.

That feeling doesn't necessarily come from film acting which, for Phoenix at least, could be a cold, lonely experience - no applause, no instant gratification. Where better to find such luxuries than behind a microphone, with the weight of a guitar on your body? Even when Island Records, who had given Aleka Attic an open-ended deal, declined to release their album, Phoenix put out a self-financed CD.

You'd think this tale of woe would dissuade Depp, who's already seen how sordid the pop world can be - after all, he appeared last year (with Shane MacGowan) on Top of the Pops. Perhaps he's trying to match rival babe Keanu Reeves, blow for blow. Reeves, who's another friend of Flea's, plays bass in a punk-grunge-thrash-metal outfit called Dog Star. They've been on British TV a few times, though you may have mistaken their music for the sound of gremlins in the central heating. The only thing listed under "relevant experience" on Depp's CV is "mates with Flea". Do you see a pattern emerging here?

There's no doubt that these aspiring rock gods - others include Bruce Willis, David Hasselhof and Kim Basinger - are taking themselves far too seriously. British actors have got the right idea. When they meddle with music, they're only having a lark: Oliver Reed bulldozing through "Wild Thing" or fouling up the sound track to Tommy; Rupert Everett simpering through "Generations of Loneliness".

P will be touring this year, by which time an album should be with us. If the staff at Notting Hill's Record & Tape Exchange have got any sense, they'll already be clearing the shelves in preparation for its arrival.