Koblo Stella 9000

Derek Johnson & Debbie Poyser explore a colourful way of applying virtual synth processing to your samples.

Danish software house Koblo haven't let the grass grow under their feet since the launch of their Vibra 9000 software synth (reviewed SOS December 1998). As well as the luminously green Vibra family (9000, 6000 and the freebie 1000), there's now the Gamma 9000 software drum synthesizer, clad in Princely purple graphics, and Stella 9000, a midnight‑blue sample playback engine that applies many of Vibra's tricks to samples of your choice. It's Stella 9000 that's under the SOS microscope this month.

Living Colour

Stella's sample import area offers basic sample‑manipulation tools.

Hearing preliminary news about Stella, we got the impression that it was to be a full‑fledged software sampler and were quite excited. When the software arrived, however, Stella's box put us right, relating how Koblo "realise the amount of work that has gone into making great sound samples around the planet" and have "created Stella 9000 to let you use all those great samples." Which makes it pretty clear that Stella isn't taking on the likes of Bitheadz' Unity DS1 (reviewed SOS April '99) and aiming to turn your computer into a hardware sampler alternative. Rather it's kind of a Vibra 9000 for your own samples, allowing them to be used as an oscillator in a Vibra‑like environment, processed with a range of traditional analogue‑style synthesis tools and generally turned upside down and inside out. Once we'd stopped being disappointed that Stella doesn't sample, we started to think that what it does do would be pretty cool anyway...

A look at its facilities reinforced this impression: Stella is 8‑note polyphonic, works in real time, integrates with Steinberg's Cubase VST 4.1 MIDI + Audio sequencer using its new VST 2 technology, provides full MIDI control of parameters (plus transmission of on‑screen parameter adjustments over MIDI), and can record its output as audio to hard disk. It offers a couple of basic sample‑manipulation tools, a wide range of synthesis facilities, and an arpeggiator. Last, but certainly not least in these times of aggravatingly ever‑increasing computer requirements, it demands a relatively modest minimum of a 120MHz Power Mac (it's not yet available for PCs) and 16Mb of free RAM. This requirement would increase, however, if Stella were run alongside other Koblo applications or a sequencer.

They've Got The Look

Though Stella 9000 offers only a single filter, it's a highly impressive one, offering unusual facilities such as comb filtering and the ability to vary the response across the stereo spectrum.

All Koblo programs have had a cosmetic redesign, but they're still unmistakably Koblo. Alterations include slightly more streamlined graphics, extra virtual LEDs, and a new virtual knob design incorporating an arrow that lights when the knob is moved. Stella looks as stylish as Vibra, and has just as straightforward a screen layout.

All the action occurs on the main screen — the only screen Stella has — though various setup functions are performed via pull‑down menus. Importing a sample simply involves clicking in the Sample section of the screen, whereupon a file selector appears and one chooses a sample from wherever it's stored. There's no restriction on the length of samples imported (other than the amount of RAM the user has allocated to the program), but they must presently be in Sound Designer II (SDII) format. This fact may raise a few eyebrows, because SDII isn't really the standard these days; Koblo even suggest gleaning samples from the Internet, and these are mostly in WAV format. All is not lost, however, since Koblo promise that WAV and AIFF files will be importable soon, via an update scheduled for early October. Meanwhile, if that update hasn't materialised and you've got your hands on the software, there are shareware programs that can convert AIFFs and WAVs into SDII, including DSound Pro, available from www.hitsquad.com/smm/. This program converts samples one at a time, but BIAS' Peak (not shareware!) has a batch‑conversion facility.

Though Stella is polyphonic, it's not multitimbral. A sample can be played with 8‑note polyphony, but there's one sound at a time only. The fact that Stella's output, single notes or performances, can be recorded as an SDII file might help to get around this limitation. The facility would allow a multi‑part performance to be built up one part at a time, and collated in any multi‑channel audio software. Stella's output can also be patched through Cubase VST 4.1 mixer inputs, so audio could be recorded into a VST Song. Also, multiple copies of Stella can run at the same time, with a different sample in each, but you'd need a powerful computer to do this as well as run VST.

Stella doesn't try to offer the sample mapping and editing operations a hardware sampler (or software alternative such as Unity) would provide: there's no facility for placing multiple samples across a keyboard, for example. The single sample that's imported is just transposed by the program as you play, and thus may be prone to artefacts at extremes of transposition, though Stella's playback engine seems to keep such artefacts to a minimum. In fairness, any weirdness resulting from overstretching one sample would only really be a problem with traditional instrument sounds, and Stella probably isn't going to be used for such sounds. If you happen to have some SampleCell‑format multisamples lying about, they can be imported and should behave properly across a full pitch range. There's nothing in the manual about this, but Koblo's Emil Tin says it's possible.

Staying with the Sample section of the screen for a moment longer, samples may also be transposed and fine‑tuned here, and have their pitch‑bend range set. The Offset control changes the playback start point within a sample, so that, for example, it could play without its attack portion. (These changes are made largely by ear, as there's no waveform display. Parameter numbers can be seen changing in a display in the Global section of the screen, however.) The Loop button either turns on a sample's loop if it has one already defined, or if not simply plays it back in a loop, end to end, until the note is released. Samples can be reversed, and there's a simple envelope generator which can be used to quickly tailor a raw sample before sending it through the synthesis facilities. This saves tying up one of the better‑specified main EGs, which might be required for other purposes. Simple velocity modulation is also offered, with a choice of four parameters that can be affected by velocity — volume, pan, pitch and sample start offset. Again, this means that you don't have to waste any of the eight modulation routings in the main modulation matrix (see next section) on these simple sound‑modifying duties.

Bend It, Shape It

The modulation matrix allows up to eight sources — including envelopes, LFOs and MIDI controllers such as aftertouch — to be assigned to a wide range of destinations.

Once a sample is imported, Stella can process it with broadly the same synthesis tools as Vibra 9000 offers. The major difference is that Stella doesn't have Vibra's two DSP‑derived oscillator models. Your sample becomes the program's oscillator and can be passed through a filter and processed by up to three envelope generators and three LFOs. The interaction between the sample and Stella's synthesis sections is defined in the modulation matrix, which allows up to eight modulators to be selected. Modulation sources include the EGs, the output of the LFOs, modulation wheel, MIDI note number, velocity and pitch‑bend. Destinations can be most on‑screen parameters (including, importantly, filter resonance and cutoff frequency). Each modulation source/destination routing also has an amount control, which varies a modulation's effect. This can itself be a modulation destination, as can many other modulation sources, which offers potential for creating complex, moving sounds from relatively simple source material.

Stella is equipped with only one filter, but it's a killer. For a start, it can be high‑pass, low‑pass, or band‑pass — or all three at once — and it offers eight types: 2‑pole, a classic 12dB/octave analogue filter; 4‑pole, a 24dB/octave type; 8‑pole, a 48dB/octave modern innovation capable of producing a sound rather like a vocal tract; double, which arranges two 12dB/octave filters in parallel; quad, which is four 12dB/octave filters in parallel; notch, or band‑reject, two 24dB/octave filters with separate low‑ and high‑pass processing; saw comb, a multiple‑resonance filter producing a metallic, digital sound; and square comb, a thinner, reedier‑sounding version of the previous filter.

Filter controls include Cutoff frequency, Resonance and Keytrack, the last altering the filter's response depending on where the sound is played, typically making a sound brighter higher up the keyboard. The filter wraps up with three controls not normally found on real‑world synths: Separation alters different filter parameters depending on the chosen filter type, such as a secondary cutoff frequency that's related to the main cutoff in the dual 2‑pole filter; Spread creates a subtle or extreme stereo image from the filter types — at least two must be turned on for this effect; and Distortion adds overdrive to the filter, varying between merely grungy and pretty nasty!

The really important thing is how the filter types sound: in a word, great. While essentially analogue in tone, when driven they produce an edge that is dynamic and digital but not unpleasant — the characteristic Koblo signature. The filter types sound very distinct from each other, and you can get a very useful range of sonic variation by combining the different types with the high‑, low‑ and band‑pass options.

Moving on to the envelopes, each of Stella's three EGs has identical parameters: attack, decay, sustain and release, plus a velocity‑sensitivity knob and an inverse switch. The last has the effect of inverting all the values in an envelope — for example, one with a fast attack will seem to have a slow attack and vice versa.

Just as Stella's filter is more sophisticated than that found on many 'real' synths, so its LFOs are also almost over‑specified. Each offers a choice of six waveforms (ramp up and down, pulse, square, sine and random), plus controls labelled 'Rate' and 'Sharp'. The former control obviously sets the speed of the LFO, though there is an option to sync it to incoming MIDI Clock (but not Stella's arpeggiator); sub‑divisions between whole and 32nd notes are available, with dotted and triplet options. The Sharp control governs the cutoff frequency of a low‑pass filter that's built into the LFO, adjusting the 'sharpness' of the output LFO waveform (but not the sample being LFO'd). Not a common feature on any real‑world synths! The LFOs also have a simple attack/decay EG, allowing the LFO effect to be faded in and out — like a sophisticated version of the LFO 'delay' parameter on many synths.

On‑screen parameter changes are made with the mouse. This has its disadvantages, including the fact that only one parameter can be tweaked at a time. The virtual knobs also require a specific mouse technique to be developed. Those with insufficient patience and deeper pockets may want to invest in a hardware MIDI controller box!

However you tweak, when a sample has been satisfactorily mangled it can be named and saved as a 'Preset'. All current screen settings are saved with a Preset, and Presets can be organised into folders. Koblo also provide around 90 factory sounds in a handful of categories (Pads, Ambience, Effects, Electronica, Instruments, and the oddly named Odd). The sounds are mainly in the spacey, sci‑fi, synthetic mould and probably more for the purpose of allowing people to try out the program than anything else.

Upside Down: The Arpeggiator

Koblo's arpeggiator implementation has been developing, in part due to user feedback, since we reviewed Vibra nearly a year ago. The result is an unusual arpeggiator, the like of which we haven't seen elsewhere. There's no user pattern creation, and it only operates in 16th notes, but the variations possible through the interaction of the controls can produce funky, if unpredictable, results. Explaining it is even more awkward than getting your head around Koblo's explanation in the manual, but using it is easy and fun — even though you don't always know why the control you're tweaking is doing what it's doing. As far as we can make out, here's how it works.

At a basic level, the usual Tempo control is provided, with a range of 0‑300bpm; synchronisation to incoming MIDI Clock is also possible. Also familiar is the Octave Range control, which allows arpeggiations to take place over up to eight octaves. Beyond these functions, however, lies unfamiliar territory! The arpeggiator works with what Koblo call Groups, of which there are four, containing 'Elements': the Key group relates to the notes held down on a MIDI keyboard, and its Elements are therefore pitches; the Octave group relates to the octave range you've set, so its Elements are different octave shifts; the Rhythm group relates to the velocity of arpeggio notes (minimum and maximum MIDI velocities only), so its Elements are note velocities; and the Slide group is rather misleadingly named, since its Elements are lengths or gate times for individual steps in an arpeggio, which create a legato‑type effect.

For each Group there are 16 preset Patterns of Elements that will govern the behaviour of the Group — Key Group patterns dictate in what order the notes held down are replayed, for example, while Rhythm Group patterns place stress on different steps in the arpeggio. (Patterns are selected by number, and no indication is given as to the effect the Patterns will produce.) Each Pattern can also have its own length (1‑16 steps), independent of the others. You can imagine the kind of complicated‑sounding results obtainable with a different pattern for each Group, and a different length for each, too.

Further GBcan be inflicted on an innocent chord by the application of the Cycle parameter (a common feature of arpeggiators in general). This parameter is available for the Key and Octave Groups only and sets whether the notes or octave shifts in a Pattern play in an upwards direction through the Pattern, downwards, or upwards and then downwards. As if all this wasn't enough, four Arpeggiator Modes are also chucked into the pot. These do additional clever things with an arpeggio, determining further interaction between the notes and octave shifts. The effect is almost like a sequencer riff‑generator.

The manual offers one very sound piece of advice: "A good way to understand and learn how to use the arpeggiator is to play with it — turn it on, play a chord on your MIDI keyboard and try to change some of the arpeggiator settings." We'd go along with that!

Magically Hip?

Stella 9000 is a fabulous sound‑design tool that should really be in a different category to software samplers such as Unity DS1. It looks fantastic and is immediate and easy to use. No knowledge of synthesis theory is required to get great sounds out of it, and because you bring in external samples it's sonically open‑ended. A wider range of sample import/export options is also on the way. It's a shame it's not multitimbral, but at least it's polyphonic, unlike Vibra. Actually, since Stella doesn't sample and is otherwise so similar to Vibra, Koblo could have considered making Vibra polyphonic and adding a sample‑import option to it. But that, of course, would have rendered Stella unnecessary and wouldn't have enabled Koblo to sell two programs...

It's not at all hard to recommend Stella 9000: we'd love to see a sampling facility, true multitimbrality, and maybe some simple effects, but as it stands the program is enormous fun and beautifully designed. Though it seems slanted to appeal to the dance fraternity, it could provide much more than £150‑worth of use and entertainment for any computer‑based contemporary musician.