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Stepp DG1 Electronic Guitar

The "guitar player's synthesiser" is now in full production. We analyse the mechanics of the Stepp, and let two musicians - a guitarist and a keyboard player - give their views on its playability.

After five years of development, the Stepp guitar has been fined-tuned into a production version. Is this the best way of controlling synth sounds using a guitar style?

The History

FOR YEARS, GUITARISTS have been looking for a way to play synthesisers without having to resort to learning keyboards. MIDI connections looked as though they'd be the answer to guitar players' prayers, yet many of today's MIDI guitar controllers have yet to overcome the tracking delay problems which prevent most players from diving in head-first into a guitar synth system.

Making life no easier is the confusion which every guitarist faces when trying to figure out which synth to use with a specific controller. The Roland GR700 system took care of the synth-matching problem by incorporating a JX3P synth into the pedalboard, but this still left the tracking problem unresolved. Yet there is little doubt that many more guitarists would get involved with guitar synths if only these matters could be worked out somehow.

The basic problem is that guitars are not naturally suited to controlling synthesisers. The easiest way to control a synth is via a simple bank of switches - the sort of thing that can be incorporated into a piano-style keyboard with no real trouble. The guitar, on the other hand, uses strings which not only produce the fundamental pitch of the note being played but also generate a host of complex harmonics which shift in phase and vary in amount according to picking intensity, picking style and picking position. The harmonic content also changes as the note decays, and with some guitar styles it's even difficult to determine a note-on and a note-off time.

The first attempt at guitar control of synth sounds (adopted by a variety of manufacturers) was to use a more or less conventionally built guitar fitted with a separate pickup for each of the strings. Ingenious circuitry was then added to separate the fundamental pitch from the harmonics - no easy task, as the second harmonic often exceeds the fundamental in amplitude. Once the fundamental has been extracted, the pitch has to be analysed and then used to drive a built-in synth circuit or to derive MIDI codes to control an external synth.

But there is a limit to how successful this method can be, as there is an inevitable delay in measuring the string frequency before it can be converted into a control signal. This is usually at least two cycles at the fundamental frequency, which can add up to tens of milliseconds on the lower notes... clearly an unacceptable state of affairs for accurately timed percussive sounds.

Currently available pitch-to-MIDI converters all suffer from this limitation to some degree, and often mistrack when the player's picking style generates a high level of harmonics.

But to this system's credit, it can be applied to a standard guitar, and the guitar's own sound can be utilised alongside that of the synth. It can also be made inexpensively and in some cases, added to the musician's own instrument.

The SynthAxe worked around the tracking delay problem by eliminating it. Rather than attempt to decipher each string's fundamental pitch, the SynthAxe uses two sets of strings: one set works as part of a switching matrix which determines the notes fingered by the left hand, while the other set senses the strings being picked, strummed, or damped.

The SynthAxe also has other unique controls, but with a retail price at £6,995 excluding any synthesisers (a must), it has been within reach of only a small number of professional musicians.

The DG1

WHEN IT CAME to designing the DG1, the people at Stepp adopted a similar approach to SynthAxe; their instrument would not be a guitar as we know it, but a device to tell the synth what the guitarist was doing with his or her fingers. They then decided to build a synthesiser into the unit so that what the player gets is a ready-to-go package that only needs an amp before it can be used to make music.

So the Stepp is futuristic in design, but it does resemble a guitar in many ways - it even has a whammy bar. The body incorporates master volume and tune controls to bring it into line with any external synths, but there is no control over the level of such synths on the Stepp body itself.

"The inside of the neck is a piece of sophisticated electronic circuitry of which the frets are only a part, and which uses over 400 components."

What is not instantly obvious from a photograph is that like the SynthAxe, the Stepp has two sets of strings, one for the left hand and one for the right. The strings are not tuned, and there are no pickups for sensing string vibration in the traditional sense. The string system is the heart of the Stepp player/synth interface and will be covered in detail shortly.

In terms of engineering, the Stepp guitar is made from plastic with a steel skeleton, and uses few (no, make that none) of the traditional guitar-making approaches. A removable knee rest makes playing easy in a sitting position, and the instrument is no heavier than a conventional guitar, so it can be played comfortably in a standing position for long periods. The quality of the engineering can't be stressed too highly, and the styling is obviously the result of a lot of thought and design expertise.

The floor stand, or Life Support Unit (LSU) as it's affectionately known, houses the power supply, the voicing electronics, the MIDI hardware and one of the three microprocessors that run the system. There are balanced and unbalanced line outputs, as well as MIDI In, Out and Thru.

The Left Hand

THE LEFT-HAND SET of strings form switch contacts with the frets, which are not metal but a specially designed semiconductor material. In fact the inside of the neck is a sophisticated piece of electronic circuitry of which the frets are only a part, and which uses over 400 surface-mounted components.

Once the string is in contact with the fret the electronic circuitry monitoring the string/fret system can detect which strings are depressed and on what frets, and can also measure the string position on the fret. The initial string contact position is interpreted by the system as being the unbent note, so sloppy playing doesn't result in notes being bent slightly. On a guitar this hardly matters, but with synth sounds, any slight tuning errors are very noticeable. If the string is subsequently bent or if vibrato is applied, this information is transmitted to the onboard computer where it is turned into digital control signals for the internal synth and the external MIDI link. And to make the left-hand action simulate that of a conventional guitar, fast pull-offs or hammer-ons allow the note to carry on as it would on a regular guitar, but lifting the finger slowly damps the string.

Thanks to the unusual string geometry, the string-bending action does not follow the same proportions as a full-length single string, so correction is applied within the software to give bending more natural characteristics. Yet even with this refinement, it can still be difficult to get enough pitch-bend at the low end of the fingerboard, while it is easy near the centre. As the bend function is software controlled, the amount of pitch-bend can be widely varied and even made negative. The result of bending a string and hearing the pitch drop is odd at first but can be used to great effect.

The strings themselves may be set at any tension that feels right, but they are all of the same gauge and must not be wound. Rotosound make the special strings needed for the Stepp, and the review model was fitted with .016" strings. This feels strange at first but you soon get accustomed to it.

The fingerboard is dead flat rather than cambered, and this too is made of a specially developed plastic into which the frets are set. Red LEDs take the place of the more usual dot markers, and of course there are no tuning pegs.

The Right Hand

THESE STRINGS DETECT plucking and muting, but due to the requirements of the electronics, you must either play with an electrically conductive pick or with your fingers; fingernails or plastic picks just don't work. This is because the action of making an electrical contact with the string opens a gate which measures the picking intensity via a series of capacitive transducers.

If you mute the string with the heel of your hand, the gate is again opened, but the new picking intensity will be zero so the note dies away at whatever rate is set up in the synth. As the inbuilt synth has been designed specifically for use with the Stepp system, it uses an ADSM envelope rather than the more common ADSR, M standing for mute.

"The right-hand strings detect plucking and muting, but the electronics require that you play with an electrically conductive pick or with your fingers."

A metal pick is provided with the guitar, but as this might not be to every player's taste, Stepp are now considering offering a full range of conductive plastic picks. How about conductive nail varnish for Flamenco players, folks?

There are actually two playing modes. The first mode, Normal, is the conventional pick-with-the-right, finger-with-the-left method. The dynamic control of the right hand combined with the pitch control of the left (string bending, hammer-ons, and so on) pave the way for some pretty expressive playing.

The second, Keyboard mode ignores the right hand altogether and simply goes by the left hand fingering. This could be useful if your left hand technique is very clean, or if you happen to be Stanley Jordan. But introduce a bit of slop, and the resulting "incidentals" which occur can be annoying. Still, if you do watch your playing carefully, you can successfully pull off some hammer-ons and retrigger the DG1.

The Synth

UNUSUALLY (FOR THIS day and age), the Stepp uses an analogue synthesiser based on the popular Curtis chips - though these are under digital control. In fact, there are six independent synthesiser voices, each dedicated to one string. Thus each string produces only one note at a time, just like on a guitar. On the DG1, however, each string can play a completely different sound, which is completely unlike a guitar.

To ensure stability of tuning, the onboard computer continually retunes the synth oscillators when they are not in use. Two oscillators are provided for each note, giving a choice of square, triangle and pulse waveforms with the usual pulse width modulation and oscillator sync features that you would find on a sophisticated analogue synth.

As you would expect, the synth is programmable and there are 100 programs in all - 10 preset, 70 user-programmable, and a further 20 user-programmable Split programs which allow each string to play any of the 80 non-split programs. So, the first three strings could produce brass sounds; the fourth string, a bass synth sound; and the remaining two strings, a Clavinet patch. Similarly, each string can be routed to different MIDI channels if extra synths are to be added to the system.

Programs are selected with a rotary encoder, and an LED display shows the currently selected program number. At first it feels odd to select programs in this manner, since in order to get from, say, program 14 to program 72, you have to pass through 58 programs. But once you've used the DG1 for a while, using the system becomes second nature, and the sacrificing of random access to any program for a simpler control panel makes more sense. If you still insist on random access to programs, then any of the MIDI foot controllers (such as the new Yamaha model) would solve this by connecting to the LSU's MIDI In.

Because the DG1 guitar itself interfaces with the LSU only, and since MIDI isn't necessarily the ideal synth control language where guitars are concerned, the internal synth uses a specially developed digital control system running three times as fast as MIDI. This accepts independent bend and vibrato information from each string and causes no perceptible delays.

MIDI signals are generated for driving external synths but the choice of synth dictates just how successful this union will be. For example, many synths accept only common pitch-bend information, so that when you bend one string, all the other notes playing at the same time go with it.

The built-in synth can also be controlled via the whammy bar, which is in reality a sprung bar connected to a ceramic pot to form an assignable modulation controller. Any of the modulation facilities can be addressed via the bar, either singly or in combination, and the system supports six different modulation sources which may be routed to up to 13 destinations. The sources are the bar as just mentioned, the strum action, the fret position (individual string bend), the LFO and the two ADSM envelopes. The modulation destinations are amplitude, pitch, pulse width for both oscillators, sync, LFO rate, both oscillator waveforms, oscillator balance, oscillator detune, noise level, filter resonance and filter frequency. As you might imagine, that gives you a lot of scope both in the sounds that can be generated and the way in which you can control them.

"Each string produces only one note at a time, just like on a guitar, but each string can play a completely different sound, which is completely unlike a guitar."

Normally the Stepp is in Play mode. But press the Edit switch, and several of the parameter switch LEDs begin flashing to indicate which parameters may be selected. Press any of the flashing parameter switches, and that parameter LED stays lit, while others may start flashing. All this is a bit confusing at first, but in fact, this is the Stepp's own way of presenting parameter menus. The lit LED indicates the menu you have entered, while the flashing LEDs indicate what your options are. When you want to edit any parameter, press the Range switch, and adjust the displayed value with the rotary encoder. Any time you wish to go back a step, press either the '*' switch or the switch corresponding to the menu you're in. Considering the simplicity of the front panel, Stepp have done an admirable job of providing programming controls for such a sophisticated synthesiser.

How does it sound? Were this synthesiser to be controlled by a standard velocity-sensitive keyboard, it would impress with its extensive modulation facilities, two oscillators, and dynamic control. Sync patches, strings, brass, and Minimoog-type sounds abound in the factory presets, and even just in the brief time we spent with the DG1, we came up with some impressive sounds you'd be hard pressed to find on most analogue synths, DCO'd or not, these days.

Other external interfaces include a tape dump of programs, and there is talk of a customising system whereby users can have the bend scaling and other internal factors modified to their specific requirements. This would be done by the dealer, and new information entered into the system via MIDI where it would be permanently stored on battery backed-up RAM.

One last but rather neat touch on the DG1 is the Chord function, which enables you to program open tunings into each patch. Each string can be detuned either one at a time, or by simply selecting the Chord function, fingering a chord, strumming the right set of strings, then pressing the Chord switch. These open tunings are reflected in the MIDI data sent out to other instruments, so that the slave synths play the same notes as the DG1. And since the DG1's strings aren't meant to be heard, there is no annoying conflict between the DG1's programmed tunings and what you'd expect to hear from the guitar itself. A limitation in the design's favour, perhaps?

The Comments - PW

SO YES, THE Stepp system avoids most of the problems found in pitch-to-MIDI guitar systems. But it would be wrong to think that a guitarist could just pick it up and play it without making some concessions; it is, after all, a new instrument that just happens to make use of the guitarist's way of playing.

Let's start with the fact that the Stepp can sound very different from any normal guitar. Because you can set up sounds with very long decay times, for instance, you may find that when you remove your finger from a string too quickly, the note continues to sound at the pitch of the open string. This is because the internal system is interpreting your action as a pull-off, rather than as a damping action. This is a particular nuisance when trying to make quick chord changes.

And when you do successfully damp a note by taking your finger off more slowly, some sounds end in a discernible thump which is difficult to avoid. I heard this effect on an Alan Murphy demo, so it isn't just my sloppy playing.

Another limitation is that pull-offs (and hammer-ons) don't work with short percussive sounds, because the action of doing a pull-off or hammer-on doesn't retrigger the sound, but merely prevents the release phase of the sound from executing. If you want to make extensive use of this technique, you need to choose a sound that has a high sustain level.

In other respects, though, I have to say that the Stepp tracks accurately and consistently, with none of that random yodelling that you occasionally get with pitch-tracking systems. But there are occasions on which insufficient string pressure results in the note lumping between the one fretted and the open string note.

The lack of any delay makes a refreshing change, especially when using short percussive sounds, and the response to playing dynamics is excellent.

"The guitar is probably not the first choice as a synth controller, but Stepp have come up with an instrument that most guitarists could come to terms with."

I found that choppy playing styles didn't translate very well, though, even if you set up the right sort of sound with fast attack - yet slower, more melodic passages sounded quite superb.

What I couldn't do in the short time that I had the instrument for review, was come to terms with the way the string-bending effort produced little result at the low end of the fingerboard, yet behaved normally in the middle. Perhaps the user customisation option will get around this.

From my personal viewpoint, the Stepp will never be the ideal instrument because I like to be able to switch between my natural guitar sound and the synth, or even to use them together. If I had a DG1, I could do things with it that I couldn't do with any other guitar synth, but I would feel forced to divide my music into songs that used synth and songs that used guitar. For that reason and that reason alone, I would still use a pitch-tracking system for gigs and live with its limitations. In the studio, though, it's a completely different story. Here you can overdub both real and synth guitar parts where they are needed, and the Stepp's superior performance can be utilised to the full.

The Stepp isn't going to be everything to everyone, but then, I can't imagine any guitar-controlled system will ever be that. As stated earlier, the guitar is probably not the first choice as an instrument to use as a synth controller, but Stepp have come up with a self-contained instrument that most guitarists could come to terms with, and which can be used to produce music previously impossible on either guitar- or keyboard-controlled synths.

Stepp would have us believe that playing their instrument is a bit like changing from a family saloon to a racing car, but I see it differently, certainly from the playing point of view. If you can imagine moving from a comfortable modern car to a classic vintage car, you would be nearer the mark. You have to learn to handle the non-synchro gear box, you have to adapt your driving technique to its peculiar little ways, and even then, you'll still be greeted by the occasional crash of gears when you least expect it.

The Comments - RD

YOU CAN'T ALWAYS judge a synth by its voices alone, and the Stepp especially is no exception. The DG1's synthesiser makes some impressive sounds, and even though I'm a bit surprised that Stepp chose analogue oscillators over digital for the DG1, I'm happy to hear those Prophet-like sync sounds again.

But what really impresses me is how the expressive control of the DG1 makes these sounds appear that much more distinctive. And one of the reasons for this is that the Stepp is one of the few electronic instruments which allow polyphonic pitch-bend or modulation, thanks to the fret modulation source. Routing the fret source to the filter cutoff or to the oscillator 2 tuning offset (while sync'd to oscillator 1) produces some amazing inflections, yet the DG1 still sounds like a guitar, simply because of the phrasing guitarists are accustomed to using.

As a MIDI controller, the Stepp is flexible enough to drive several synths independently, and the enabling of MIDI controllers, program changes and so forth make it as powerful as any keyboard controller I've played. The DG1 may not be intended as a controller for external voices, but it'll probably get a lot of use as one. And it'll be interesting to hear some of the sounds players will make when the DG1's analogue voices start blending with samplers and other digital synths.

Programming the Stepp may be a challenge for many guitarists, but if independent programmers take to the DG1 as they have with the synths that came before it, there should be plenty of sounds available before long. And since the DG1's programming controls are a bit cryptic, I won't be surprised if some editor/librarian programs start popping up for the usual computers.

Since the DG1 requires a conductive pick to trigger properly, I can foresee that many guitarists may have a hard time initially. Similarly, there are many left-hand techniques which do not translate perfectly from normal guitar to the DG1. It would be nice if hammer-ons retriggered the synth voices, and bending strings in the lower frets could be easier. Since fingernails aren't very good conductors (no excuse for sticking them into power outlets, though), fingerpickers will need conductive finger picks, or shorter nails so they can use their fingertips. That aside, I couldn't perceive any trigger delays, and this alone makes the Stepp a joy to play.

Keyboard players have been changing their techniques to get the most out of their instruments for years now, and will probably continue to do so as long as new instruments emerge. Nobody would consider playing a strings sample the way they would an acoustic grand pano, for example.

Of course, guitarists will have to alter their playing technique to get the most out of the DG1, but considering the advantages, I think plenty of guitarists will be prepared to do just that.

The DG1 is a very expressive instrument, and though its retail tag keeps it beyond the budget of the majority of guitarists, I can see it making its way into the hands of many guitar players who are really serious about marrying their technique with new sounds.

Price: £3500 excluding VAT

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Songs From Four Strings

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Sight Reading

Music Technology - Copyright: Music Maker Publications (UK), Future Publishing.


Music Technology - Feb 1987

Gear in this article:

Guitar Synthesizer > Stepp > DG1

Previous article in this issue:

> Songs From Four Strings

Next article in this issue:

> Sight Reading

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