With the U20, Roland have introduced yet another term to the hi-tech vocabulary - Resynthesised Pulse Code Modulation - and another slick, cost effective keyboard to the market.

IS IT A synth? Is it a sampler? Is it, perhaps, a bird? No, it's an RS-PCM keyboard instrument, and it's playing at a music shop near you soon. RS-PCM stands for ReSynthesised Pulse Code Modulation, a technique new to Roland instruments whereby PCM-encoded samples are, ahem, resynthesised.

As its name suggests, the U20 is related to Roland's U110 PCM Sound Module (reviewed MT, January '89), a multitimbral sample replay expander, hence the PCM tag. In fact, the crudest definition of the U20 would be that it's a U110 with a keyboard tacked on, but in terms of features it's both more and less than a U110 (mainly more), and stands as an instrument in its own right rather than a simple repackaging exercise.

The first thing that strikes you when you play the U20 is how clean it sounds, much cleaner than the U110, in fact. This cleanness is apparently down to the U20's superior internal processing, which shouldn't be confused with the new RS-PCM technique that it employs. In fact, it's not at all clear what advantage RS-PCM has over the U110, which uses straight PCM sampling. And unfortunately the U20 manual's flimsy explanation of this new technology doesn't make us any the wiser. No-one's asking to be blinded by science, but I can't help feeling Roland owe it to their customers to provide a better explanation than "RS-PCM uses Roland's unique technology to analyse, modify and 'resynthesise' the PCM-recorded instrumental sound. This results in a realistic sound that can be controlled in musically appropriate ways". Wow and triple golly gosh.

Overview

THE BASIC UNIT of the RS-PCM sound generator is the Tone, namely the sample data. The U20 has 128 onboard Tones, divided into Piano, Vibraphone, Bell, Marimba, Guitar, Bass, Choir, Strings, Organ, Wind, Synthesiser and Drums categories. If you're a Roland U110 sample module owner, these categories might seem familiar; in fact, the U20 provides you with many of the U110 samples plus an added section of synthesiser sounds.

Further Tones can be accessed from ROM PCM cards. In fact, the U20 can read existing U110 PCM cards, of which there are currently seven available from Roland, via its two rear-panel PCM card slots.

At this point you may be wondering: if the U20 sounds cleaner than the U110 what will U110 samples sound like on it? I wasn't able to check this out, but according to Roland they sound as clean as the U20's onboard samples, because any noisiness on the U110 was introduced by its internal processing.

Although the U20 is 30-voice polyphonic, in practice the polyphony depends on whether the Tone you're using is single (68 internal), detuned (25), dual (20), velocity-mixed (9) or velocity-switched (6) - obviously, single and velocity-switched allow 30-voice polyphony while the other types allow I5-voice. And, of course, when you layer Tones you reduce the polyphony even further.

Organisationally, the U20 is divided into five sections: Setup, Keyboard Patch, Sound Patch, Timbre and Rhythm Set. The Setup section is for global parameters, here you can set the master tuning, adjust the LCD contrast, and define a variety of MIDI transmit and receive settings. A U20 Sound Patch consists of six Parts and a Rhythm Part, ie. a multitimbral configuration. You can select one Timbre for each Part, a Timbre consisting of a Tone plus parameters governing level, pitch and vibrato modifications to that Tone. These are the only modifications you can make to a U20 sample. Unlike Korg's M1 and Ensoniq's VFX synths (both of which draw on samples as their raw sound material) and unlike Roland's own W30 sampler-based workstation, the U20 has no filters. Meanwhile, for the Rhythm Part within a Sound Patch you can select one of four onboard programmable Rhythm Sets. The U20's voices are allocated dynamically across the six Parts and the Rhythm Part, but you also have the option to reserve voices for individual Parts (so that a prominent musical line needn't be robbed of voices at a crucial moment).

A Keyboard Patch allows you to program the four front-panel Performance functions (keyboard transposition, chord play 1 & 2, and arpeggio play) and to define various MIDI transmit channel options. Onboard the U20 you have access to 64 Sound and 64 Keyboard Patches, while further Patches can be accessed from a RAM card which can be plugged into the U20's rear panel. One Sound and one Keyboard Patch can be active at a time, and can be selected independently or together from dedicated front-panel buttons. In this way you can, for instance, vary the Performance function settings for a single Sound Patch, or select several different Sound Patches while keeping the same performance settings.

The Rhythm Set section allows you to program a "drumkit" across the keyboard, with each key drawing on any one of the 128 internal Tones or PCM card Tones. In this way your "drumkit" isn't restricted to traditional drum and percussion sounds - you can incorporate tuned percussion, bass sounds, horn sounds, anything you feel is appropriate.

The U20's five-octave, synth-style keyboard is sensitive to attack and release velocity and channel aftertouch (though the instrument's sounds can also respond to poly aftertouch via MIDI) and has a comfortable yet substantial feel. To the left of the keyboard are the familiar Roland bend/mod lever and a volume slider, together with two control sliders, which can be programmed to allow realtime editing of internal sound and effect parameters and/or transmission of MIDI controller data during performance. And, unusually, you can program separate bend up and bend down ranges for the lever.

The U20 comes complete with a feature common on keyboard instruments nowadays, namely onboard digital reverb and chorus (the U110, you may recall, was limited to chorus and tremolo). You can route individual sounds through the reverb only, the chorus only, chorus and reverb, or bypass the effects altogether. For chorussing, the U20 allows you to select from chorus 1 & 2, FB-chorus, flanger and short delay effects, with level, delay time, rate, depth and feedback all programmable per patch. The reverb settings provide a choice of three rooms, two halls, gated reverb, delay and cross delay (repeat delays pan left and right), with associated time, level and feedback parameters. As generally seems to be the case with onboard digital reverb, you get neither the sophistication nor the quality of a professional stand-alone unit, but while professional studios might shun these effects in favour of their Lexicons and AMSs, they are perfectly adequate for the home studio setup. Incidentally, anyone not wanting to make use of the onboard effects can switch them out globally.

Roland have provided large and informative LCD windows on recent instruments like the W30 Music Workstation and A50/A80 MIDI Keyboard Controllers, but the U20 sticks with the more familiar two-line backlit LCD. Also familiar is the low-profile, minimalist front panel layout which is becoming something of a Roland trademark.

Operationally, the U20 is similar to the U110, with a limited set of buttons leading you through a hierarchy of software pages. However, because there are many more pages on the U20, this approach can get a little tedious, so Roland have included the jump function which they introduced on the W30. In this way you can assign 16 software pages to the Bank 1-8 and Number 1-8 buttons, and jump straight to any one of them by pressing the jump button followed by the relevant page select button. A welcome feature.

Rear panel connections offer MIDI In, Out and Thru; two PCM sample card slots (whereas the U110 has four slots on its front panel); one RAM card slot for patch storage; a sustain footswitch input; programmable control pedal jack input; stereo headphone jack; and four audio jack outputs configured as two stereo pairs. One pair (L/mono and R) transmits an effected signal while the other is a dry output. You can selectively route U20 sounds to either pair, and sounds routed to the effected pair can be made to bypass the effects, allowing you to include a dry sound within the effected stereo (or L/mono) output.

From a musician's point of view the variety of audio output options on Roland's instruments can be rather bewildering. After all, everyone wants as many outputs as possible, but what you get ain't necessarily what you want. The realities of cost and of marketing strategy have the final say. For instance, the more expensive U20 loses two outputs compared to the U110, but then it gains onboard digital reverb. The most obvious division of labour across the two stereo pairs is to separate out the drum sounds from the instrumental sounds, taking some or all of the former out via the dry pair for external processing. Multiple dry mono outs might have been preferable in this context, but for anyone wanting to route the U20 directly into a portastudio or into, say, an eight-channel mixer, I guess the dual stereo configuration strikes an, er, effective balance. The other advantage the U20 has over the U110 in this area is that you don't have to contend with the latter's convoluted voice output assignments.

Tones, Timbres & Multitimbres

THE U20'S SOURCE samples, known as Preset Tones, all exhibit great clarity and presence. Roland have provided a good range of familiar instrumental sounds, multisampled where necessary. These include ten acoustic pianos (ranging from soft to bright to honky-tonk), seven electric pianos (with warm, smooth and bright, percussive versions), five acoustic guitars, six electric guitars (including muted and distorted versions), several vibes and a marimba, 12 slapped basses (with harmonics in the upper range), one nicely woody double bass (with fingerboard noise mixed in when you play hard), a couple of beautifully warm, rounded fretless basses, eight punchy synthbasses, the usual (for Roland) strong array of electric organs, impressive choirs and ensemble strings, some reasonably realistic saxes and trumpets, and a varied array of synthesised sounds including bells, harps, synth choirs, Jupiter brass and strings, pulse and sawtooth waves, and even Native Dance (remember that D50 patch? This is along similar lines).

The next step is to assign one of these Tones to a Timbre and either use it as is, or twist it around a bit using the U20's Level, Pitch and Vibrato sections. These allow you to do such things as impose a different ADSR amplitude envelope on a Tone, specified as +/- offsets from its default envelope (altering the attack time is a familiar way of altering the character of a sound), determine the detune depth of detune-type Tones, add auto pitchbend, and modulate the pitch using triangle, sine, square, sawtooth (up or down), trill 1-4 or random 1-4 waves, with programmable rate, depth, delay and rise-time. You can also specify velocity and aftertouch sensitivity for all of these sections. Using these editing options, you can come up with some surprising variations on what start out as familiar sounds.

Once you've decided on the Timbre(s) you want to use, you can set up a Sound Patch multitimbral configuration to play them within. As I mentioned earlier, the U20 provides you with six Parts plus a dedicated Rhythm Part. Each Part can be assigned one sound (Timbre), while the Rhythm Part can be assigned one of four programmable "drumkits" (Rhythm Sets). Each Part can be given its own MIDI receive channel, key range and velocity "window", allowing you to define a wide range of textures. You can also program a volume level (1-127) for each Part and the Rhythm Part, and a pan value (+/-7 or random) per Part - in the case of the Rhythm Part, each key can be given its own pan assignment. However, in practice the U20's multitimbral glory isn't immediately apparent, because for most of the instrument's factory Sound Patches Roland have turned off Parts 2-6 and the Rhythm track (by setting their MIDI Receive channels to off), assigning just Part one to the keyboard.

With the U20 Roland have come up with their most sophisticated "drumkit" implementation yet. Each key in the range B1 to D7 can be assigned any one of the instrument's onboard or card Tones (and any pitch of that Tone), together with its own level, velocity sensitivity, envelope mode (sustain or no sustain), ADR amplitude envelope (allowing you to shape a sound specifically for the Rhythm Part), pitch transposition (+1/-3 octaves in semitone steps, together with +/-50 cents fine-tuning in cent steps), separate channel and poly aftertouch sensitivity, pitch randomise value (so that each time you play the sound it will be at a different pitch - a great feature for both pitched and unpitched sounds), auto bend depth and rate, detune depth, output assignment and pan value. That little lot doesn't leave much to be desired.

Another neat Rhythm Set feature is the ability to assign an alternative "mute key" to each key, allowing one key to automatically mute another when played; the obvious uses here are for open and closed hi-hats, or for retriggering a note (ordinarily a new voice will be used each time you replay a note), but bearing in mind that you can incorporate all manner of instrumental sounds into a Rhythm Set, it's a potentially far more creative feature than you might think. Also, using the pitchbend lever, or inserting pitchbend values into a sequencer track, to change the pitch of drum and percussion sounds in real time can be extremely effective, and greatly enhances the sonic variety of the U20's "rhythm section". And by zeroing the volume on selected keys and assigning sounds on an external drum machine or sampler to those same keys, you can effectively incorporate external sounds into your U20 "drumkit". Incidentally, instead of having a straightforward reverb on/off switch for each key, you can take advantage of all the output routing options - effected or dry stereo pairs, reverb only, chorus only, reverb plus chorus, or dry within the effected stereo pair. All in all, then, the U20 provides pretty impressive opportunities for inventive rhythm programmers.

To play Parts on the U20's keyboard, you must set the keyboard to transmit and the Part(s) to receive on the same MIDI channel. If you've set up a multitimbral configuration in conjunction with a sequencer, the easiest thing is to adjust the keyboard transmit channel to the Part you want to play. Alternatively, with the U20's MIDI Local function set to off and your sequencer's soft Thru function switched on, you can control what Parts you play from the sequencer's track assignment(s). Incidentally, a neat keyboard transmit feature is the ability to assign a velocity range per Keyboard Patch, so that for instance you could tailor the velocity range to the response of a particular internal sound or external sound, or even set a fixed velocity for playing, say, bass and snare drum parts.

So what sort of "arrangements" does the U20 allow you to create? As an example, you could have the Rhythm Part being played from a sequencer on MIDI channel 10, Parts one, two and three used to create a piano/bass split with the piano doubled by strings, all set to MIDI channel one, while Part four is used for a synth lead sound. You could assign a voice reserve value of one to Part four, so that the accompaniment Parts can't choke off your solo just as you're getting into full stride, and route the Part via the dry outputs, panned left or right, for external processing.

Of course, as always, these flights of multitimbral fancy will be brought swiftly down to earth if there simply aren't enough voices to go round the Parts - for instance, if you're playing five-note chords using two layered Parts, that's ten voices if both Tones are single or velocity-switched, 20 voices if they're both detuned/doubled/velocity-mixed. Still, the U20's complement of 30 voices is pretty much the maximum you're going to get out of any synth or sampler at the moment.

Incidentally, you can call up Keyboard and Sound Patches from a sequencer via their own programmable MIDI receive channels, or call up individual Timbres by sending patch changes on the relevant Part channels. To change effect settings and the output routing of different Parts, you'll need to select a new Sound Patch, while to change the MIDI performance effects you'll need to select a new Keyboard Patch.

Performance Functions

ROLAND'S DESIGNERS seem to have a partiality for keyboard peformance functions. Me, I'm not so sure, though Chase Play has always been an interesting effect (not on the U20, though - it hasn't been implemented).

The U20 offers Transpose, Chord Play 1 & 2, and Arpeggio functions, each of which is programmable per Keyboard Patch and accessible from a dedicated front-panel button for ready selection. Arpeggio has a straightforward implementation, with programmable rate and a choice of up, down, up and down or random directions; unfortunately the rate can't be synced to an incoming MIDI clock, nor are MIDI clocks transmitted. But perhaps the most interesting effect is Chord Play. Roland's Alpha Juno 1 and Alpha Juno 2 synths featured a Chord Memory function which allowed you to program one six-note chord and play it from any note (transposed accordingly). The U20 allows you to program a chord of up to eight notes for each semitone within the octave, effectively taking you into the realm of arrangement. The chords themselves aren't limited to an octave spread, but can be any collection of up to eight notes played on the U20's keyboard. Up to eight of these Chord Sets (collections of 12 chords) can be programmed into the U20's internal memory. You then assign, per Keyboard Patch, a Chord Set to each of the two Chord Play buttons, which allows you to quickly switch between two "arrangements". You can also set a key offset for each Keyboard Patch, so that the same Chord Set can be used for playing in different keys, while because Chord Play is a monophonic function (no spontaneous bitonality here, I'm afraid), you can set the retrigger mode to off, low or high. When more than two notes are held down on the keyboard, retrigger determines which (if any) key and associated chord will be triggered when you release the sounding note. Unusually, the velocity of the retriggered chord is determined by the velocity with which you release the first chord's key.

The notes resulting from each of these Performance functions are transmitted via MIDI, and so can be recorded as part of a sequence and/or doubled on other instruments (the arpeggio function even has its own MIDI transmit channel assignment). However, you can't trigger these functions from incoming MIDI notes (interestingly, the Alpha Juno's Chord Memory function allowed you to do this - so why not on the U20?). Another shortcoming, it seems to me, is the fact that the Arpeggio and Chord Play functions apply to the whole keyboard when selected - a programmable key-range parameter wouldn't have gone amiss.

Finally, Roland have included an altogether more esoteric function in the form of a MIDI Monitor page which allows you to see incoming MIDI data (with or without MIDI real-time messages) or MIDI data that is being transmitted from the U20's keyboard. This data is placed in a 256-byte buffer and scrolled across the U20's LCD window as it's received; you can also use the Part +/- buttons to scroll in either direction through the buffer's contents yourself. All very handy, you might think, but there is a catch: due to the window's limited display capabilities, all data is displayed in hexadecimal notation. Whoops, user-friendliness goes out of the window (literally).

On a more positive note, Roland now seem to have wholeheartedly adopted the index as an integral part of their manuals, as do an increasing number of manufacturers. Perhaps my days of moaning about indexless manuals are over at last (and not before time).

Verdict

HOOK THE U20 up to an external sequencer and you've got a well-thought-out and flexible multitimbral sequencing setup, complete with powerful rhythm facilities and, with the addition of the U110 Latin and FX percussion PCM ROM cards, a solid if largely unadventurous range of drum and percussion sounds to draw on. The inclusion of digital reverb and chorussing and the dual-stereo output arrangement make a lot of sense for the musician on a budget who is perhaps recording direct onto a personal multitracker rather than onto 24-track tape via a 32-channel mixer. It's really the home musician of relatively modest means, and the newcomer to musical technology, that the U20 is aimed at.

However, there's a danger that the U20 might end up falling between two stools (or, if it's anything like a certain MT editor, two bar stools). Why? Well, it's neither a sampler nor a synth, and although the relatively limited editing facilities and the ability to layer sounds do allow you to "transcend" the source samples to some extent, it's still basically a matter of what Roland decide to provide you with in the way of internal samples and U110 PCM sample cards, is what you get. Consequently, to a large extent you're dependent on Roland's idea of what sounds you should have. In comparison, Ensoniq's new VFX synth really lets you play around creatively with sound, get between the cracks and subvert the sort of creeping compartmentalisation offered by an instrument like the U20. And Korg's M1 synth, which like the U20 allows you to access further samples via plug-in PCM ROM cards, lets you use its samples in their natural state or put them through a full-blown synth section. Meanwhile, any sampler will allow you to incorporate and use in your music whatever sounds you see fit. Personally, I hope that the U20 isn't the forerunner of a new type of keyboard instrument which limits your sonic choices. There may be a "preset culture" among musicians nowadays, but that doesn't mean manufacturers should pander to a mentality which they have helped to create through convoluted digital-access editing systems. Rather, they should concentrate on providing much better editing access - open up, don't restrict.

So is it to be the sample playback of the U20 or the more sophisticated sonic manipulations of the M1, the VFX, or Kawai's new K1 II synth? Let the musicians decide.

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