YOU'D NEVER KNOW IT to glance through the brochures, the price lists and the advertisements, but there are currently two general trends in electronic pianos. Some have a myriad of gadgets and features such as easy-play facilities, rhythm sections, sequencers, and built-in effects. Others concentrate on providing a "pure" acoustic piano sound and a keyboard action that is closer to the real thing.

As a rule, though, neither type of piano is particularly cheap. Gone are the days when an "electronic" piano meant two hundred quid's worth of cruddy sounds and tacky plastic keys. Today's equivalents, especially the grander, more "classical" instruments with their sturdy cases, digital sounds and weighted keyboards, can cost literally thousands.

The idea behind these new Casio CPS pianos seems to be this: strip away the effects, the auto-accompaniment features, and the rest of the silly add-ons, and you've got an electronic piano that may not have quite the sound or keyboard quality of the pseudo-classical models, but sells for an awful lot less. In other words, they're simple, functional pianos aimed at musicians who prefer to indulge their own playing ability rather than that of their instrument.

Let's start with the keys themselves. The CPS700 keyboard is not quite as wide as that of an acoustic piano, with 76 notes (that's six octaves plus a minor third, theory buffs). However, this is the standard size for many electronic piano keyboards, and the missing notes don't hinder you too much. The CPS300 has only five octaves, which helps to explain why it's £100 cheaper. In all other respects, the two keyboards are identical. They're both unweighted, which means they are less like an acoustic piano, more like a synthesizer. They continue the Casio tradition of being very light to play - which won't suit anybody who wants to retain their conventional piano technique, but might be useful to those who've been brought up playing piano, but now want to acquire a smoother, lighter touch more in keeping with hi-tech instruments.

In addition to being lighter to play than many electronic pianos, these Casios are also a good bit lighter to carry. This, together with the fact that they can be both mains and battery operated, means that if you need a piano to take out on the road (or even on the streets), these have to be major contenders.

Of course, the main reason anybody considers buying instruments like these is that they want something that sounds like a piano. And the sound labelled "Piano" on the CPS' front panel is quite an authentic example of the electronic breed; it has plenty of brightness and sparkle, though it also has a tendency to sound mechanical.

There are four other sounds on both these instruments: Harpsichord, Vibraphone, Electronic Piano and Pipe Organ. They won't break any records for being realistic, but they're a far cry from the indeterminate murmurings produced under similar names on portable keyboards. The Harpsichord sound is a little thinner than you might expect, but the Vibes give a good warm sound. As for the Electric Piano and Pipe Organ, they're a bit toppy for my tastes but you, of course, may beg to differ.

The usual sockets are available on the back panel: headphones (for keeping your inadequacies quiet), audio out (for connecting to an external amp and improving the sound quality), and MIDI In/Out (for connecting up to other electronic sound sources). If you want to tune either of these pianos to other instruments - something no acoustic piano can do, remember - the rear panel also houses a pitch control.

If you're new to the whole business of playing keyboards, both these pianos feature what Casio call a "Music Library". This consists of note data stored within each instrument's electronics, and briefly enables you to select a pre-recorded piece of piano music from each white key on the keyboard. The piece is then reproduced with note-perfect precision by the piano: either you can listen to it to find out how it should be played, or you can play along to it to see just how far short your performance is, and where all the mistakes are. Casio also provide a book of all the piano scores in the Music Library, all of which are recognised by the Associated Board of Music and graded according to their exam scaling.

Because the keyboard on the CPS300 is slightly shorter, the music library is commensurately smaller. And in both machines, the pieces are presets that cannot be altered or replaced. Nevertheless, they offer a valuable service not provided by any other manufacturer of electronic pianos.

If you're after an affordable electronic piano professional enough to produce convincing performances, then the CPS series could be just what you need. It's impossible to give more than a general idea of what they sound like or of how their keyboards play, and these things are vitally important - so track one down and try it out!

CASIO CPS300 PIANO: £399; CPS700: £499; both including VAT

INFO: Casio Electronics, (Contact Details)