We were amazed and decidedly sceptical when we heard of the Thompson Vocal Eliminator. The UK distributors claim that, suitably interconnected with your hi-fi, it will remove the vocals from records played through it. Really wild, huh?

It apparently does this by mucking around with the phase — like when you mistakingly connect up one pair of speaker leads the wrong way round and get no bass from your speakers and an annoyingly thin overall sound. But at a little over 200 quid, the VE1 Vocal Eliminator is something of an expensive phase-modifying toy. And after trying one out, our scepticism remains.

First things first — why get rid of vocals anyway? Perhaps we could practice our singing over fave tunes without the false security of harmonising with the real singer? Or, a little more interestingly, we could investigate more closely particular instrumental parts behind the singer, once all the screaming and shouting's out the way. And that would seem to be about it.

People have tried this sort of thing before. Kenny Everett has certainly used a similar device on his radio show in order to play vocal-less records on the air. And the trend even spread to a few companies releasing records of tampered-with multitracks (a totally different idea, of course) such as EMI's Beach Boys greatest hits without vocals. The Beach Boys without vocals. Great! Next: Sunny Ade without percussion. But I digress.

The VE1 is a long thin hi-fi-gadget-shaped hi-fi gadget, with but six knobs on its dark fascia. There's a bit of wood at each end so that you can't put your hands inside.

The easiest way to connect the thing is to your amp's tape in and out sockets, so that you can switch the thing through by activating your tape monitor switch. Other methods are detailed in the manual which comes with the Eliminator.

So on with a record, and this is what you do.

As well as the on/off switch, there's a switch to change between the original record's sound (vocals and all), and the modified (hopefully) vocal-less sound. To its right are the main knobs with which you adjust the gadget to get maximum elimination of vocals, and these are marked Vocal Cancellation, Lows and Highs. Straight away we discover the machine's major weakness.

It won't remove the vocals from every record you play through it. In fact with the records I tried, instances of total vocal elimination were very much the exception rather than the rule one would expect from something quite clearly labelled "Vocal Eliminator".

Certainly the Lows and Highs knobs are very sensitive, and small turns will result in relatively big changes in the presence or otherwise of the vocal. Sometimes you manage to affect the vocal sound hardly at all; sometimes it's diminished and drifts into a semi-distorted mess somewhere further back in the modified mix; sometimes you can totally rid yourself of vocal cords.

But the other problem is that you don't just affect the vocals. Presumably the machine 'assumes' that vocals are in the centre of the stereo/phase picture, and it consequently does away with other central or prominent sonic detail such as strong instrumental lines or solos. Sometimes, anyway. Sometimes not. Indeed it's an unpredictable machine.

Other controls balance the level of the modified sound against the original sound, and alter the tone quality of the modified sound. The manual suggests that you should use these controls to enable you to 'mix' records back and forward between modified and original sound, and to match the original sound's tonal make-up. The first use didn't interest me, and the second I found impossible.

This is because the consequence of meddling with the phase is not only to remove or diminish vocals and other instruments, as mentioned just now, but also largely to do away with any bass element such as electric bass guitar, synth bass, bass drum, or whatever else is lurking deep down in the mix. So to attempt to restore the tonal balance of the original sound by a simple pair of bass and treble controls is rather pointless.

I tried lots of records: from the Sixties I had success with the Beatles' 'I Feel Fine', and was able to get rid of the vocal entirely from 'I Wanna Hold Your Hand', revealing coarse guitar chords and little else. But many Fab Four tracks wouldn't 'work', which slightly surprised me as I had a strange suspicion that 4-track recordings might somehow respond more readily to the machine. But I think I have crossed wires there. It's phase relationship that matters to the VE1 (I think...).

Into the Seventies, and Steely Dan's 'Kings' is an interesting one — a little knob-turning loses Fagen's vocal (and the spiffing guitar solo, alas) but keeps the female backing singers. Interesting to hear what they were actually up to.

A similar trick was possible in the Eighties, where Duran Duran's 'Lonely In Your Nightmare' came out without Le Bon, thus highlighting the still-existing sundry backing vocals. And on XTC's 'Senses Working Overtime' Andy Partridge's voice is removed except for a few brief seconds toward the end of the track when he suddenly says what sounds like "Striking me...". Then he's gone again. How significant. Perhaps it means he's really dead, struck by an assassin's knife...

For all these minor successes, however, there were plenty of records which wouldn't work, either partially or thoroughly. The 'Trouble Shooter Checklist' that comes with the VE1 does actually admit, right up the back, that 25% of records will be "borderline or unusable". I'd say nearer 50%, or more.

If this was a £20 toy box I'd gladly have one around for dull moments. But at £215 (plus VAT) it is seriously overpriced. At this level one expects some sort of consistency, but with the techniques involved I don't see how this can be guaranteed. Let's hope the manufacturers, LT Sound in the Southern United States, can do something about it. Or perhaps a DJ Eliminator. Or a Blues Guitarist Eliminator. Or an Offensive Sequencer Eliminator. And so on.

£215