The decision to concentrate on digital synthesisers can't have been an easy one for Yamaha. It involved breaking away from the analogue system everyone else was using and spending untold thousands investigating FM oscillators.

FM stands for frequency modulation, and without getting too technical it's a digital technique that goes up in tiny, even steps in order to reach the level you want.

Yamaha's first forays into this area produced the phenomenally expensive GS1 and GS2 keyboards. They had a magnificent sound but limited appeal because of the price and because they couldn't be programmed.

With the CE20, it looks as if that research could finally be paying off for those of us whose wage packet is not written in telephone numbers. This synth combines six polyphonic settings each handling a maximum of eight notes with 14 monophonic settings. They are all presets covering acoustic instruments — flute, trumpet, piano, etc — and in many cases they are superbly realistic.

True to Yamaha's boast there is very little that's electronic about the CE20. The sounds are pure, and remarkably natural. The keyboard itself is both touch sensitive — the harder you hit it the louder or brighter the note will be — and second touch responsive — add a little extra pressure and effects such as vibrato will be faded in.

These performance facilities coupled to the sweet sound make it one of the most expressive synths I've played in a long time. It's lovely.

The CE20 is quite compact and slim, no more than 33in long and 11½in deep, finished in matt black for the top half and panel, with an imitation teak surround on the bottom. The 49-note C-to-C keyboard is smooth, silent and easy to get on with. The monophonic voices include piccolo, flute, oboe, clarinet, saxophone, two trumpets, trombone, violin, cello, two contra basses and two electric basses. The poly section handles brass, horn, organ, electric piano, harpsichord and strings.

Each voice has its own effects programmed in, so employing the second touch facility will produce a result realistic to that instrument. But you can override the preset and there are six sliders that let you set effects manually.

The tone-initial determines how bright the note is when you first hit it, tone-after raises the brightness when you press down on the second touch, vibrato comes in at the same time and there are depth, speed and delay controls for it.

There are also overall brilliance, volume and pitch sliders, plus a chorus ensemble dubbed "symphonic" that is actually silent, smooth and effective. The final control is a wheel at the left of the keys, not for modulation but to alter the speed of the portamento. A switch with an integral LED above it brings in the glide and the keys sense when you need it.

Play one note at a time and nothing happens, but press a new key while still holding down the last and THEN the portamento will come in — again a great boon to expression, especially on the horn and trombone settings. The glide only works on the monophonic voices.

As for the sounds themselves, the piccolo is high and pipey, the flute beautifully rounded, rich and breathy. Oboe, clarinet and sax are all harsher, reedier voices, not quite so successful, but the two trumpets are excellent — the first is bright and orchestral, the second is slightly muted and more full bodied.

The touch sensitive keyboard is set so that if you hit the note fast it will introduce an initial overblown blare to all the brass sounds — something that is an essential part of their character, but which I have never heard any other synth capture.

Trombone is just as good, though an octave lower, and sounds magnificent when the glide is on. Violin and cello are disappointments but the Contra basses are winners, the first having a soft attack and a long sustain (you can almost hear the bow being drawn across the string), the second is like a plucked double bass with a slow decay. The electric basses are both tighter sounds and on the second, the harder the key is hit, the more slap you get from the bass.

Polyphonic brass is fine at high, stabbing lines, but the horn is the best sound on the keyboard. It's smooth, big and gentle, and even has a hint of white noise to recreate the breath of the horn player.

The organ is high, bubbly and jazzy, and could have had more bottom end, and the piano is very Rhodes-like, even introducing the metallic clank of a heavily belted tine bar when the keys are played hard.

Sometimes, though, this piece of touch sensitive trickery didn't trigger properly when the sustain footswitch was on. Harpsichord and strings are both mediocre.

The major adjustment to make is that the CE20 doesn't produce the huge, multi-oscillator brass and string sounds of Prophets and the like. It's a cleaner, more precise instrument, closer to true orchestral textures than it is to rock brass or string sections. Also it's more inclined towards sedate and slightly romantic lead lines than it is to fierce jazz/rock soloing or techno-pop percussion.

The CE20 is a vindication of Yamaha's experiments with FM synthesis since the lessons they learned on the GS1 and GS2 have been applied to this wonderfully playable item of gear.

It almost seems cruel to describe it as a machine. It is, I think, a modern gentleman's instrument.

£999