In pop and rock music, sound is all about fashion. One year jangly guitars are in, another it's syndrums, gated drums, DX7, fretless basses, Prophet 5, D50 bells, M1 breathy vox... all come, and go, within a year or so.

But through it all, from skiffle to soul, from jive to modern jazz, from hip hop to house to heavy metal, there's always been a place, somewhere, for the sound of an acoustic piano. Throughout not just pop's history, but as far back as the beginning of the 18th century, the acoustic piano — the sound of felt hammers hitting strings mounted inside a large wooden box — has beguiled and bewitched generations of music lovers.

While there have been countless modifications, improvements, and developments (Britain's Broadwood was a prime shaker and mover, replacing the awkward knee-lever with the modern sustain pedal in the late 1700s) the essence of the sound produced by the acoustic piano has remained remarkably unchanged.

It's pointless trying to conduct a full analysis as to why this instrument, above almost all others, has found so direct, long-lasting, and universal a route into our souls, but part of the reason surely lies in its completeness, and in its infinite degree of expressiveness. The harmonic potential of each note is different. In turn, the sound of each note is almost infinitely variable by velocity. There is the interaction between played notes, and the interaction between played notes and 'open' strings, ie. unplayed notes when the sustain pedal is on. The net result is that even in exceptionally poor hands, it is almost impossible to render the sound boring or grating. There's far too much harmonic activity for the ear ever to grow weary.

If you can imagine the processing power needed to assimilate such variables — never mind the mechanical aspect of the instrument — you can see why the digital piano can never be, for the immediate price-to-processing power future at any rate, anything but a cut-price alternative.

Early attempts at reproducing the instrument electronically were mainly based upon tricks like replacing strings with reeds or rods, bashing or plucking them with suckers and rubber hammers, and using pickups to convert the results into piano-type sounds. Notable early electric pianos like the Fender Rhodes series, or the Wurlitzer EP200, while hardly authentic replicas of the piano sound, nonetheless captured something of its essence; despite hailing from the '50s and '60s, they continue to be played today primarily because they do feel like living, breathing musical instruments. Play one and you most certainly have not played them all. There are good 'uns, bad 'uns, ones with dead spots, temperamental ones, absolute peaches, and, most notably, no two players will ever quite sound the same on them.

In the 70s, thanks primarily to a legion of rent-a-marque Italian companies, the vogue was for electronic pianos — instruments that relied upon electronics for the generation of their sound, the keyboard being reduced to a mere switching device. With... ah, umm, no exceptions, electronic pianos were God-awful, and seemed so even then. Now, mercifully, you're unlikely ever to face the prospect of an Elgam Snoopy or a JHS Pro 6, so you'll just have to take my word for it.

The silicon chip, which stood the synth market on its head in the late 1970s, would, of course, soon do the same for the 'electric piano'. Early digital pianos like Yamaha's splendid PF10/15 merely rehashed contemporary synth technology. But soon dedicated piano technology, and ultimately sample-based technology, started to appear. The 1980s became the decade of the digital piano. Everyone was at it, from all angles, and at all prices, shapes, and sizes: home pianos, stage pianos, piano modules, MIDI kits for acoustic pianos. And let's not forget the stand-alone piano sample, of which it's probably fair to say Emu's EII boasted the most sought-after example.

Post boom and bang, life in the piano field is decidedly more precarious, not the least because manufacturers, in an extraordinary display of own-hand biting, quickly took to including top-notch piano samples on their seemingly dedicated synths, and on home keyboards. The main piano patch on Roland's E70, for instance, would have won awards on a stand-alone digital piano only a handful of years ago. Korg's M1 piano has surely appeared, vamping away on that blasted major ninth/seventh routine so beloved by the house boys, on more records over this last four years than did even the glossy DX7 'electric' in its heyday back in the early 1980s.

Such progress is all well and good up to a point, the point in question being that at which the sound of an acoustic piano becomes fossilised in a cruel caricature of its true self. Part of the problem of piano sounds on synths goes deeper than the current glut of cost-cutting and job-sharing. It concerns the validity of simply chucking sample memory around and tossing in the odd slice of 'string resonance' sample. Yes, the results impress when you first hear them. But after a while the inherent sameness of all sampled pianos begins to wear.

ACTION

Are we perhaps better off with the attempts at vaguely piano-like tones on a more responsive instrument? Certainly I can understand Elton John's genuine love affair with Roland's RD1000. Not the best piano sound, technically, by a long chalk. But, like the Rhodes and Wurli before it (though not for the same reasons), the RD feels like a living, breathing instrument.

The key word here is 'feels.' No matter how spanking the sample, if the feel is wrong it will be difficult, if not impossible, to achieve the best results. This is true of all instruments to a degree, but the sound of an authentic piano part is partly a product of the level of exertion required to produce it. A simple test: next time you're in a studio alongside a grand piano, play an identical 'piano' part on the grand, and then on a lightweight synth action keyboard using your best piano patch. I guarantee that you'll play more notes — play a busier part — on your synth, because you feel you have to work harder to achieve the same effect.

The action of an acoustic piano is a complex mechanism. Of a piano's 6,000 or so parts, 75% are devoted to its action. The overall balance, weight, and all-important escapement — the mechanism that releases the hammer so that your finger has no direct contact with the hammer at the moment it actually hits the string — is a product of the fundamental design. Recreating the feel of all this is always going to be a problem.

Although each manufacturer of digital pianos claims to have found the answer, some using springs to force back the keys, some definitely not using springs, there is no consensus of opinion as to which, if any, type of design inherently works or feels best. One test of an action's authenticity is to measure the number of repetitions it is capable of, in other words how many times (per second) a key can be struck and still produce its note. A figure of six times per second is thought standard on an acoustic piano.

CURRENT TRENDS

If it makes somewhat depressing reading to see how few dedicated hi-tech or stage digital pianos are currently on the market (and just a single module, Emu's Proformance, although Yamaha have indicated that they may re-introduce their handy little EMT10), we can take heart from the level of interest that manufacturers are currently taking in keyboards and keyboard action.

All instruments in our survey, with the exception of Akai's piano sound board for the MX1000 master keyboard, now sport 88-note keyboards, and almost all carry some fancy moniker to highlight the legitimacy of their 'genuine piano action.' Talk is cheap, however, and marketing ploys even cheaper. No amount of techno waffle should ever convince you that something feels any different to what it actually feels like to you.

With a piano, more than any other keyboard purchase, there is no substitute for sitting down and playing the instrument for as long as it takes you to decide that this feels right for you.

Sympathetic string reverberation, the effect of open strings 'singing' that you can hear most clearly on an acoustic piano by stamping on the sustain pedal, is a current hobby horse, and one that can provide a pleasing level of accuracy if handled sensitively. Unfortunately, some manufacturers are so pleased at having discovered the effect that they can't help but splash it all over, producing instruments that just sound noisy.

As with all keyboards, polyphony is on the increase. A full piano part, ie. a two-handed affair with possible use of the sustain pedal, will certainly benefit from a polyphony of 24 voices or more, to avoid note shut-off. The table overleaf is a comprehensive guide to all the digital pianos on the market.

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