Every home should have one, that's my opinion. Many would agree that there is no electronic instrument around that is quite as versatile as the digital sampler. Synthesizers are often claimed to have an 'infinite' range of sounds, but the infinity of possibilities open to a sampling keyboard, or module, covers a much wider range - from the cliche of barking dogs to the more recent cliche of snippets from old movie soundtracks, and everything in between.

As is to be expected, samplers are becoming more and more sophisticated. Once it was sufficient for a sampler to be able to play back a sound at different pitches, and to be able to assign different samples to different areas of the keyboard. Now the emphasis is on the ability to manipulate sampled sounds - using filters, envelope generators, and any other technique that the designer can think up. It isn't enough for a sampler to have multi-megabyte memory or super-high sampling rates. It's the sample processing power that is becoming more important.

The snag is that power of all kinds can be difficult to harness. We all know the difficulty of trying to manipulate an instrument with a brain the size of a planet, when all you have at your disposal is a tiny LCD window and a handful of data entry buttons. Developments in instrument technology demand matching developments in the user interface. We need more control.

THE S550 SYSTEM

The Roland S550 sampler comes in a 3U rack-mounting box which needs more than just a MIDI keyboard to get it going properly. To make the system into a fully functioning life-form, two more pieces of equipment are necessary - a video monitor (RGB or direct video input) and a mouse (there is also an optional remote controller, the RC100). The S550 can be used with just a keyboard for performance, but for recording and manipulating samples the monitor is essential. The mouse is optional but very useful.

So, to be a successful S550 captain, you need to be in control of four pieces of hardware. But more than that, you need software too. The Roland S550 comes without an internal operating system, so this needs to be loaded, each time you power-up, from floppy disk. This is no inconvenience, and has the advantage that when Roland think of some bolt-on goodie to add to the S550, all you need is a disk containing the new operating system and you can update your machine.

"Total available sample memory of the S550 is impressive. At the higher 30kHz sampling rate you'll squeeze in 28.8 seconds of sound."

Spec-wise, the S550 is a 12-bit device which, despite the availability of Casio's 16-bit FZ1, seems to be adequate for most users' purposes. Sampling rate can be either 15kHz or 30kHz. You'll get a frequency response of just under 15kHz at the higher rate and just under 7.5kHz at the lower. If you remember that the Compact Disc system samples at 44.1 kHz, you will appreciate that this isn't the hi-est of fi, but for most musical purposes it's quite good enough. My feeling is that we are limited by the floppy disk storage medium more than anything else. The greater the sampling rates and number of bits, then the more data is generated. This all has to be stored somewhere, and floppy disks are slow enough at loading and saving to make most people just the weeniest bit impatient. More data would simply make things slower still.

Total available sample memory of the S550 is impressive. At the higher 30kHz sampling rate you'll squeeze in 28.8 seconds of sound. Not bad, and that is two 3.5 inch DSDD floppy disks' worth. Unfortunately, this doesn't mean that you can record one overall sample as long as that. There are two memory blocks, each of which is divided into two banks. So, if you are into epic samples, there is room for four at 7.2 seconds each. If short samples are your preference, then up to 64 sample locations of 0.4 seconds (0.8 seconds at 15kHz sampling rate) are available.

Before I proceed, a few words on vocabulary are necessary. If the Oxford English Dictionary provided a few technical definitions, then manufacturers wouldn't have to invent a new system of nomenclature every time they produced a new sampler. So, those of you who are more at home with maps or keygroups, take a lesson in Rolandspeak:

- A newly-recorded sample (virgin sample?) is called a WAVE.

- A Wave can be processed to form a usable version of the original sample, which becomes a TONE, and is stored in one of the 64 Tone locations.

- A SUB TONE is pretty much the same as a Tone, but it 'borrows' Wave data from a Tone. It uses up a Tone location, but it doesn't take up any sample space.

- A PATCH refers to the way Tones are spread out over the keyboard. There can be 32 different Patches stored in the S550's memory.

- A VOICE MODULE is the section of circuitry that plays the Patch and directs it to an output socket, There are eight of these separate outputs, so you could play eight Patches at the same time, possibly over different MIDI channels. Each Voice Module can be assigned to any of the eight outputs.

Have you got that? I'll test you later. I can tell you that it took some figuring out to glean all this information from the manual. It's the familiar situation where once you understand the machine, you understand the manual! When will they cease to be manufacturers' afterthoughts?

"The S550 is a 16-voice machine... if you are playing several Patches at the same time over different MIDI channels, then voices are assigned automatically. You don't have to specify six notes for this sound, two notes for that, or whatever."

An important point, which Roland have failed so far to publicise sufficiently, is the dynamic voice allocation system. The S550 is a 16-voice machine, meaning it can play 16 notes simultaneously, which isn't bad. More important, if you are playing several Patches at the same time over different MIDI channels, then voices are assigned automatically. You don't have to specify six notes for this sound, two notes for that, or whatever. That's a good point in itself, but even better is that it works for all of the eight outputs. So, you can have a different Patch coming from each output polyphonically. To put this in perspective, the Akai S900 can only play one note at a time (monophonically) from each of its individual outputs. The Roland way is much, much better and they don't seem to be bragging about it yet. Having said that, you can allocate specific numbers of notes to different Patches if you want to, but who wants to?

Also available is a choice between first note priority and last note priority. 'First note' means that when you have 16 notes playing, any new notes will be ignored. 'Last note' means that as new notes come in, the oldest ones are sacrificed to make way. Both possibilities have their uses.

SAMPLING

I have already mentioned that the S550's basic operating system comes on disk, and disks containing sample data can conveniently contain system data too. What I didn't say is that several functions have to be accessed using an additional Utility disk. That includes sampling.

The provision of sampling as an 'outboard' capability may seem strange at first, but what Roland have done is to separate the function of sample taking and manipulation, and the function of performance. For the former, you need a MIDI keyboard, a video monitor, preferably a mouse, and definitely a Utility disk. For performance you need just the MIDI keyboard, the unit itself and a couple of sample/Patch disks.

Let's go through the sampling procedure and the possible manipulation techniques, paying special attention to the benefits offered by the video display...

The starting point for sampling is to insert the Utility disk and call up the Utility menu from the main menu. Does it sound a bit like operating a computer? It certainly feels like it. When 'Sampling' is selected from this menu, the appropriate screen appears. This is shown in Figure 1. As you can see, the screen asks for sample - sorry, I really must start calling it Wave - Wave location details, and details such as the original pitch and the trigger threshold. At the bottom of the screen is a level meter, which does a pretty good job of telling you whether your sample will overload or not. There is also a limiter function which is supposed to prevent overload, but I tried it and it didn't.

There are three ways of triggering the recording process. AUTO and MANUAL are self-explanatory, but PREVIOUS is a Roland master-stroke. Select this and the unit continuously records into its memory, for up to 7.2 seconds if you wish. When the mouse button is pressed to take the sample, the data that is already in the memory is frozen. So what you do is listen until you hear something you like, press the mouse button, and you've captured it! OK, so Roland didn't think of it first, but if I give them a lot of praise for including this feature perhaps all the other sampler manufacturers will include it too. It really is very useful.

Once the sample is taken, the video monitor display changes to show the waveform in the memory - in fact, the waveform of the entire Wave Bank - and the remaining sample time.

The next step in the procedure is to TRUNCATE. Call it up from the Utility disk. The waveform of the sample is displayed together with two cursors showing the start and end points. It is very simple to edit a sample from this screen, moving the points around while playing the keyboard. And when you've got it right, execute the function and you have a nice, neat, truncated sample. Sorry - Wave.

"Going one better than some samplers, the S550 lets you assign a Tone to any combination of keys, not just ranges of adjacent keys."

One nicety that Roland have missed is that they could perhaps have had a cursor travelling across the screen as the sample plays. It's difficult to tell from the waveform exactly which part relates to which part of the sample. Of course you can distinguish sound from silence, but not a lot more than that. It is perhaps worth remembering that future software updates could change this.

Next on the list is LOOP. Anyone who has a sampler will probably have spent many a happy (?) hour looping their samples. With the S550, once you have puzzled out the ramifications of the looping process, it will be much easier. There is the obvious advantage that you can see what you are doing on the waveform display (Figure 2 shows a loop with both a visible and audible click). More importantly, you can hold down a key and listen to the loop repeat itself as you adjust. You don't really have to watch the screen. When you have found an audibly good loop - which will take approximately two ticks - then you can look and confirm that you have joined points of equal level and approximately equal slope. You can even zoom in (magnify the waveform) and see how wonderful it looks on the display. To me, it is the hearing that is important. Doing it on the S550 really is simple. From the one screen, the start and end points of the loop can be set using coarse and fine adjustments. Loop points can be moved either by shifting one end or the other, or by moving the loop as a whole to different parts of the sample, keeping its length.

What if the sample is mostly OK but has a slight glitch somewhere in its length? For this you might call up the WAVE DRAW utility. This doesn't really mean drawing a waveform from scratch, but modifying an existing waveform to cure some problem it might have. Once again, there is a waveform display. This time it can be directly redrawn using the cursor, under mouse control. It sounds good in theory, but in practice I found things difficult. I sampled a couple of seconds from a record (naughty, but just for a test!) containing a click. I should have been able to redraw the waveform to exclude the click. The only problem was finding it! Once again, if there had been a cursor travelling across the screen as the sample played (to help you reference where you were in the waveform with the sound), it would have been a lot easier. As things stood, it was hard work. But it is still a useful facility to have. I can imagine radio producers taking samples from sound effects records and using this function to edit out the clicks - and there are usually plenty!

So far, so good. Yet another utility which I was quite taken with was the digital filter. This doesn't work in real time, but processes the data to achieve what an analogue filter could, but probably with reduced sound quality. Remember that filtering on a synth or sampler is a high speed activity, which is far more difficult to do well than static filtering like on a mixing console.

Highpass or lowpass filtering is possible with variable resonance, so you can achieve resonant effects much like on an old-fashioned analogue synthesizer. The standard filter slope is 12dB per octave, although the filtering process can be repeated to get a steeper slope value. Level is also adjustable. This is necessary because raising the resonance could raise the volume level of the sample, which could possibly overload the system.

Although I like the digital filter, there is one quibble. Why isn't frequency measured in Hertz? And why isn't resonance measured in standard Q values? I could also ask why the Level Adjust function doesn't come in decibel steps. The point is that these are all units that we have become used to. If each manufacturer has his own system, then we will not know where on earth we stand. This is an important matter and I hope Roland will attend to this in a future software update. It really would be useful.

There are other functions in the Utility mode which are worth investigating, such as MIX and COMBINE. 'Mix' obviously mixes two samples. 'Combine' takes part of one sample and glues part of another to it. I wouldn't count on doing tricks like joining the attack of a piano to the sustain of a sax though. You can't hear what you are doing as you do it (!), so it promises to be a lengthy procedure. I didn't achieve anything worthwhile.

TONES & PATCHES

So far, I have been describing functions which affect the Wave - ie. the original sample - either by changing the Wave directly or writing an altered version into a new location. However, changing Tone parameters does not affect the original sample data. The Tone can always have its original settings restored.

The most interesting Tone parameters are the Time Variant Filter (TVF) and Time Variant Amplifier (TVA). These are analogous to the VCF and VCA you might find in a conventional analogue synthesizer. Here, because they are digitally controlled, the new names are needed.

Figure 3 shows the TVF screen. As you can see, there is a graphic display of the envelope of the filter. Thank goodness for it too! Setting 8-stage envelopes numerically is a procedure on a par with the twelve labours of Hercules. I'll bet he's glad they didn't have envelope generators in his day! The numbers are there if you feel you really need them. Before I begin telling you how to edit the envelope using the mouse, I'll describe the basic filter functions:

CUT-OFF is the frequency at which the filter starts to bite. It's a conventional lowpass filter, so the lower in frequency this is set, the more 'fizz' is removed. RESONANCE controls the amount of boost at the cut-off frequency. Many other samplers, though they have filters, are lacking in this important feature. Merely filtering a sound can make it dull; adding a little resonance can put the life back into it. The LFO (low frequency oscillator) can also control the cut-off point of the filter, giving you those lovely Seventies wah-wah effects. The cut-off point can also be made to respond to keyboard velocity.

Setting the break points of the envelope generator is a mouse-essential task. You can't do it graphically with the cursor buttons on the S550 itself, only numerically. By pointing the mouse cursor at a break point on the screen and clicking the mouse button, you can move the break point, click again, and you have a new envelope. The sustain point can occur at any position in the envelope, so you can have filter variations concentrated before the sustain phase, or after you release the key, or in any combination. Being able to hear the filter changes as you make them is obviously an important advantage over the digital filter I mentioned earlier, which has to recalculate data.

The TVA also has an 8-stage envelope which can be set in a similar manner. Both the TVF and TVA have several different keyboard curves, so the way they respond to velocity can be set to your preference.

I quibbled earlier about the lack of units on the digital filter display. Again, if the envelope display was calibrated in milliseconds, it would be easier still to manipulate.

Once you have a collection of edited Tones, the next step is to create a Patch. As the S550 is capable of storing 32 Patches, it is possible to obtain several uses out of one set of Tones. For instance, you could multisample a piano, then use the same samples to create a conventional piano sound, together with (say) mellow piano and honky-tonk sounds. Or perhaps you might have a string Patch and a flute Patch, together with a third Patch which combines the two. There are many possibilities.

Most modern samplers will let you assign one or more samples to each key. The S550 allows two, which may be combined in several ways. NORMAL offers the conventional one-sample-per-key method. VELOCITY SWITCH is good for that slap bass sound, where you have a thumbed bass sample playing at low key velocities, and a 'snapped' sample which plays at high velocities. This is an either/or situation, though the threshold velocity where the changeover takes place is programmable.

VELOCITY CROSS FADE is where one sample gradually gives way to another as the key is played harder. For this, it is nice to use soft samples and loud samples. Any acoustic instrument exhibits a change in timbre (tone) as well as volume when played louder. Velocity Cross Fade makes it possible for the sampler to imitate this.

AFTERTOUCH ASSIGN is a nice feature, where aftertouch (keyboard pressure) can control the LFO, volume, or pitch bend up and down. Some other features are listed in the separate panel.

When assigning Tones to different parts of the keyboard, the video display really comes into its own. Having a picture of the keyboard means that you don't need to worry about MIDI note numbers. In INFO mode, any split points already set are displayed. Hit any key and a little blob appears on the screen to show you which note you have pressed. In SET mode, when you press a key you can either place a Tone on that key, or remove it. Going one better than some samplers, the S550 lets you assign a Tone to any combination of keys, not just ranges of adjacent keys. Thus, you could have one Tone on all the white notes and another on all the black notes if you wanted.

IN PERFORMANCE

The Roland S550 has a well and truly split personality, between editing and performance. To achieve any sort of sample or Patch manipulation, you must have a video monitor. For performance applications, the S550 will give you enough information on its tiny fluorescent display.

The only snag is, where do you draw the line between editing and performance? Suppose, for instance, you wanted to use the S550 as part of a MIDI system. You might want to use it to build up a composition using different Patches you have already set up and stored on different disks. The multiple polyphonic outputs, and the fact that you can play eight Patches at once via MIDI would seem to make the S550 ideal. The strange thing is, that you cannot load a Patch from disk together with its samples (Tones). You have to load a Patch, find the 'Split' page and see which Tones it needs, then load the necessary Tones into the correct locations. You need the video monitor to do this. It cannot be done from the S550's own display.

I suppose the way things work is that the more functions a piece of equipment has, the more scope there is for not getting them quite together. It's infuriating that Roland give you so much, but not quite the whole lot. The Akai S900 sampler, which I mentioned before, doesn't have the capability of playing more than one Patch (which it calls a Program) at a time, so the problem doesn't arise. The S900's eight individual outputs are not polyphonic anyway, so it wouldn't be of that much use. Roland have gone a big step further than this, but I don't think they have quite appreciated the direction in which they are headed.

Give me the S550's multiple polyphonic outputs and the ability to play eight Patches at once. Add to that the ability to load Patches one by one together with their Tones, from separate disks if desired. Then I would have one instrument which could truly function as eight separate instruments via MIDI (subject to the overall 16 note limit). Whether this could be a future software update I don't know. I suspect it could, but time and inclination have to be willing.

CONCLUSION

Roland have started something big. A mouse and a video monitor might give the S550 the 'Fairlight look' but they are definitely very useful. Expect more electronic instruments to sport these features too, soon.

The Roland S550 is well up in the big league of MIDI samplers. As it stands, it is an excellent machine. For ease of control and the versatility of the display, it's way ahead of the competition.

[Software versions reviewed: Roland S550 version 1.01; Roland S330 version 1.00.]

Prices S550 £2300, RC100 remote £250 ; S330 £1384 (all inc VAT).

Contact Roland (UK) Ltd, (Contact Details).