Drum machines do not often yelp like an overheated Dachshund. When one does there are two possible explanations – you have been programming a 16-beat digital dog or a Linn fitted with new special effects chips.

Linn drums and their relatives have been around for several years, long enough for us to dignify them as self-possessed instruments and forget what they are at heart – sample machines.

Linns, Oberheims, Drumulators all work on the same principle. Real drums are digitally recorded onto chips then played back by programming electronics. True, you're limited to the Factory's recordings as you can't sample your own sounds into the memory (Simmons are about to crack that nut). But why be stuck with drums? Anything can be sampled, and many strange devices can act as percussion instruments.

To this end, the American Linn company have produced scores of new, 16-pin chips that can be dropped into holders on the Linn circuit boards. And these contain sounds as diverse as unison horn sections and a slamming door.

In investigative mood, we grabbed the nearest local Linn and started popping the 16-pinners into place.

A large chunk of the new catalogue is, in fact, alternative drum sounds including the latest bass drums, hi-hats, toms, etc. For example, there's a tight and barking Simmons-esque snare (are we allowed to say that? Well that's what it sounded like) and a matching hi-hat with a larger-than-life slice of white noise and woosh taken in to recreate that synthesised effect. There's an about-turn for real life sampling.

I liked the mellower jazz hi-hats and snare whose subtle rings made a pleasant break from the normal 150 per cent thwacks and crashes.

Choice of chip is not enough, however. Positioning within the Linn plays a large part. Because of the nature of digital recording, each drum playback needs a calculated degree of filtering to account for the variations that occur during the digital capture. Therefore you CAN exert a fraction of control over the final tone by swapping the chips about within the machine.

But on to the special ones. Nearly all the samples are short. That's why drum machines are so well suited to digital recording because, apart from the cymbals, they don't demand problematic lengthy sustains as would, say, a decaying piano note.

Therefore Linn's choice has been directed towards the percussive. The first silicon into the slots was the funk bass guitar. The logical position on the circuit board is the tom holder as the front panel controls then allow you to set three tunings, enough to drop a simple, slapping bass line underneath a bass drum, for example. Like all these tunable 'instruments', they're best below a drum pattern as an enhancement. This is not a sneaky sequencer.

The funk guitar is stranger. The Linn catalogue offers you minor, major and seventh chords, plus octaves. The octaves are perhaps the safest as they can work their way across several parts of a song without fear of foul clashes. The version I heard sounded unsettlingly like an electronic banjo rather than a pokey Strat. But take the tuning down to its lowest extremes and you're gifted with a bizarre, clanging six-string that sounds as if it ought to be leading a funeral procession. Powerful and more useful than first listening might lead you to believe.

Most of the newcomers reacted well to being twisted in pitch, and don't feel that just because you buy a small item of plastic with the word 'piano' on it, that's all you're going to get. Experiments with the grand created an impressive, grumbling boing in the lower registers, for example.

The horn sections were less successful. Maybe it's just my ears, but most sampling machinery I've heard always seems to have trouble coping with saxes. The Linns were distraught and nasalish without the power you might expect from half a dozen gobs shaking the reeds about.

But the timpani – brilliant. Thundering skins that leave digital FM imitations far behind. And again, when you tweak the tuning upwards, away from norm, the results are inspiring – partly Octabanish, partly steel drum.

The selections come in three "sizes" – one chip sounds for the shortest samples, two chips where you need to capture the ambience of a tom and four chips for the full sustain of a cymbal of hi-hat. The sign of a canny company that they're giving users what they want even if it be (swallow pride) samples of other manufacturer's drum machines.

To list the entire Linn collection would take another page, but to give you an idea there are now 21 snares from the "original" to a superb wooshing, backwards recording, several rimshots, ten bass drums (TR808 and DMX clones included), sound effects ranging from temple blocks, through Phillipino dance sticks to water drips, plus a score of concert, synth and electronic toms. Finally there are the three basses (rock, E slap, G slap), six guitars, four horns, four pianos, two kotos, two synths and a vocalist going 'do'.

But while we're on drum machines, Drumulator owners should make a point of hearing the new 'rock kit' chip. It's among the latest Drumulator releases (see Shredder, P84). You only get eight sounds instead of the normal 12, but you won't be wanting any more. The spare memory space is required to store the ringing ambience of each drum, and the sound is collosal. Recorded, seemingly, in a mile-wide, disused warehouse, they are not be played anywhere that has problems with avalanches. Bigger than a Tandoori for two.

single: £40
double: £52