Few companies have done as much to further the cause of the personal keyboard as Yamaha. Their unique experience in both domestic and professional musical instrument fields has given them a built-in advantage over many rival manufacturers, in that they alone have found it possible to incorporate untried innovations without first have to research the necessary groundwork. It comes as no surprise therefore to find that Yamaha's personal keyboards often seem to be first in incorporating a certain facility or two, and the PS-55 is a prime example of this, as it includes within its catalogue of features a rhythm generator with digitally-sampled drum sounds and a sequencing/recording facility whose sophistication is unmatched in this price area.

By way of introduction, it should be mentioned that the 55 lies at the top of a range of four PS models, of which the other three are the 15, 25, and 35. A four-octave C-to-C keyboard provides the 55's starting-point, and while this may seem prohibitively small in the context of professional performance, for most possible home applications it works well enough.

Either side of the keyboard are the two built-in stereo speakers, these being rated at 5W maximum output (impedance six ohms) and having a diameter of 12cm. Underneath the left-hand speaker is the 'fill-in' press-tab, of which more later.

Control Panel

Above the keyboard lies the main control panel, which spans the entire width of the instrument and contains myriad numbers of push-switches, sliders, and LED indicators, as befits a top-of-the-range model.

Working from the right, the first major control section is that for the Yamaha's 'Solo' voices. There are sixteen of these monophonic sounds, selected by eight dual-function switches, and broadly speaking these range from the sublime (Chimes, Rock Guitar) to the almost entirely unusable (Trumpet, Saxophone). As is so often the case with Yamaha keyboards, it's possible to combine two or more of these voices simply by pressing the appropriate buttons simultaneously, although it should be noted that all the sounds remain monophonic regardless.

In addition to an on/off selector and an individual volume control, the solo section also has three effects sliders for Vibrato Depth, Sustain, and 'Celeste'. Several of the solo voices have vibrato built-in to them, and the Vibrato slider can be used either to increase the effect's presence on these sounds, or to add vibrato to those sounds no so-equipped. Like Vibrato Depth, the Sustain slider has five fixed positions, so that infinite variation of rate is not possible. However, this is of little consequence in practice because the settings provided give the user a sufficient range of adjustment. It's really the addition of Sustain that makes most of the Solo voices tolerable, though adding too much can result in some fairly gross distortion from the built-in speakers. 'Celeste' is a complete misnomer because while it might be expected to introduce some sort of percussive envelope to the preset sound, it in fact does nothing of the kind, producing instead a mild low-frequency boost to thicken up the voices. Or at least, that's what the user's manual claims it does. In reality, its effect - even with the slider at maximum - is almost imperceptible on most voices, and experimentation with another model proved there was nothing technically wrong with the review sample. Very mysterious.

Moving to the left, the Orchestra section is configured in much the same way as the Solo one, with the obvious exception that the voices are fully polyphonic. Again, these voices vary enormously between the best (Marimba, Piano, Harpsichord) and the worst (String Ensemble, Music Box). You will gather from the foregoing that, while Yamaha's percussive voices (both mono and poly) are excellent, some of their sustained-note sounds require some fairly drastic surgery if the PS-55 presets are to achieve anything approaching consistency.

It should be mentioned that combinations of Solo and Orchestra are possible and in fact positively encouraged by the manual, and in a sense this encouragement is justified since it's in this mode that the PS-55 sounds at its most impressive, and where the gap between it and so many of its competitors begins to widen appreciably.

PCM Drums

The real clincher though is the 55's rhythm machine. This offers sixteen preset rhythms (with five different fill-in variations for each), and all of these make use of PCM sampled drum sounds. Of these, bass-drum, snare and the optional handclap are the most striking, toms in the main being a little indeterminate. Despite the lack of any opportunity for user-programming, some of the rhythms generated by the drum-machine can compare with anything produced by purpose-built devices costing thousands. Generally speaking, it's the Disco and Rock rhythms that are the most effective.

Disappointingly, the Yamaha's auto-accompaniment features aren't quite up to the level of the rhythm machine, though to make up for this is the fact it's possible to record any pieces up to 800 notes in length using the instrument's Music Programmer.

First things first, though.

The first octave-and-a-half of the 55's keyboard forms the Auto Bass Chord section, and the facilities provided here include Single Finger Chords, a non-programmable Arpeggiator, and a Duet function which introduces a two- or three-note harmony to every note played on the right-hand (melody) section of the keyboard.

Memory System

The music programmer is a means of storing bass chords, Solo, and Orchestra lines, recording them one by one and layering them one on top of another in much the same way as you would overdub on a multitrack tape-machine. In a sense it's quite similar to the programmable memory system on the Casio CT-7000, though it's not quite as logical to use because the switches are not arranged in tape-recorder fashion as they are on the big Casio.

This isn't to say the music programmer is difficult to use - in fact, it's a piece of cake to select 'Off', 'Record', or 'Playback' for each of the three instrumental sections, and build up an arrangement section by section. The unfortunate aspect of the programmer is that, as on so many other personal keyboards, it is synced up to the machine's rhythm generator, which makes designing the memory chips much easier and cheaper but does limit the system's creative applications.

Conclusion

Despite its several minor failings, I don't think it would be an exaggeration to say that the PS-55 is one of the best personal keyboards currently available. Its designers have not included playcard or bar-code playback systems at the expense of the basic tonal and percussion sounds, and I think their decision is the right one. I only hope Yamaha continue to follow the paths opened-up by the PS-55.

The Yamaha PS-55 retails at £529 including VAT, and further details should be available from Yamaha Special Products, (Contact Details).