Terratec Axon AX100 MkII

The AX100 MkII system. Here an old split pickup is being used on the guitar, but any GK-compatible split pickup can be used, or alternatively, one is available from Terratec themselves (the AIX101).Photo: Mike Cameron

Take Blue Chip's advanced Axon MIDI guitar system, bundle it with new editing software and a Terratec soundcard, and you have the new Axon AX100. We strum its sounds and test its triggering...

The quest for the perfect guitar-to-MIDI controller has been a long one, and there's probably still some way to go yet, but the 1U rackmount Axon AX100 MkII system adds a new dimension to existing pitch-tracking technology. Built around the technology developed by German company Blue Chip (see the SOS May 1998 review of the Blue Chip Axon AX100), the AX100 MkII uses 'Neural Net'-derived algorithms to enhance the speed and accuracy of tracking, enabling the device to work out the initial pitch of a note based on the shape of its picking transient, so that the system locks onto the note pitch very fast. Once the note is playing, more conventional pitch-tracking technology is then used to follow it. This technology was used in the older Axon AX100, but the latest incarnation is the AX100 MkII, which includes many features not present in earlier models, not to mention a lower price tag.

Bits & Pieces

The AX100 MkII can be bought as a complete system including a suitable split magnetic pickup for use with your guitar, the necessary connection cable, and a footswitch, or you can buy the main rackmount unit on its own if you already have a suitable pickup. The AX100 MkII is compatible with Roland's GK-series pickups and also with piezo systems that have Roland-compatible electronics (from manufacturers such as RMC, and they're also used on some Godin, Fender and Brian Moore guitars). Additionally, the AX100 MkII can be used with bass guitars (with up to six strings), violins and cellos providing they are fitted with suitable split pickups. The MkII unit is fitted with an internal GM/XG soundcard as standard, and unlike some other guitar synth systems, the performance when using internal sounds and external MIDI modules is the same, as both use standard MIDI for communications. The card includes a 128-sound GM patch set and can also store 32 user patches. For modifying the sounds, there are 42 effects on the card, incorporating all the usual suspects: a rotary speaker, plus echo, flanger, phaser, and distortion modules. There are also separate reverb and chorus effects, as per the GM standard.

Software & Features

A software editor is supplied that runs under Windows or Mac OS and I had no trouble getting it to run on the latest version of Mac OS Tiger (10.4.3). It's also possible to update the AX100 MkII's operating system by downloading new versions and replacing the old ones. As well as making patch editing easier, the software provides access to all the setup functions, with sliders to set the individual string sensitivity, so adapting the system to your playing style is most easily done while sitting in front of a computer. You need a basic MIDI interface for two-way communication, but that's all.

Some of these features were present in the original Blue Chip Axon AX100, including the ability to translate picking position (string distance from the bridge) into controller information to modify sounds or effect splits and crossfades, but these functions are now much easier to set up with the new editing software. New to this model is a two-line, 16-character display for displaying patch names or editing data, and in default mode, there's a tuner bar at the bottom of the screen that shows the current note pitch relative to a centre cursor denoting correct pitch. Alternatively, the tuner can be replaced by a level meter, which aids setting up.

As with all such devices, there are several parameters that have to be set by the user before the system is properly playable. Most of these relate to the individual or collective string sensitivities, which in turn depend on the pickup spacing from the strings and the playing style of the user. There are also global sensitivity controls and a global note-off threshold, but Terratec have recognised that some performers will have two or more guitars fitted with compatible pickups, so the settings for up to four different guitars can be stored.

The AX100 MkII rack unit itself is straightforward, offering only a 'very 1988' two-line parameter access LCD and a few self-explanatory buttons and controls.Photo: Mike CameronThe sound-splitting ability of the Axon AX100 MkII is actually very clever and utilises more of that neural-net technology to allow the unit to sense the picking position along the length of the string. Sounds may be split across groups of strings, which is handy when you want a bass sound on the lower couple of strings, or you can split the sounds by picking position or fretting position. In pick split mode, up to three different zones can be created and the zone boundaries specified by the user. What's more, all the split modes can be used in combination to divide the guitar into a dozen different zones accessing 12 different sounds. Furthermore, pick positional information can be converted to MIDI controller data and sent out to control the soundcard or synth allowing you to, for example, adjust the filter cutoff frequency based on whereabouts on the string you play.

For controlling external MIDI modules, the MSB/LSB Parameters can be set to facilitate the sending of the correct bank change information and there's also a new triggering mode that retriggers a note when the pitch is bent up to (or down from) the next semitone. In effect, this allows you to get new, full-velocity notes when you hammer on or bend notes. Auto Quantise is also a feature I haven't seen in other models of guitar synth. In effect, this assumes you want to quantise your performance to chromatic pitches unless you deliberately bend a string, in which case the system recognises your intent and bypasses the quantisation to allow you to continue playing smooth bends for the rest of the note duration.

Having used a few guitar synths in my time, I have come to appreciate that the Hold pedal is a very important control for performance as it allows chords to be sustained or notes held while you action a difficult change. As usual, there are several ways you can program any attached pedal to work and this information is saved along with the patch, as is the pitch quantisation setting.

Hold Sound mode lets you program a different sound which you can set to sustain while you play over the top of it with your main sound. By holding down the pedal, you access your new sound, and then, if you hit a chord and release the pedal, the new sound will be held indefinitely (or until you operate the pedal again) allowing you to play your main sound over the top. There's also an Arpeggiator option that forces the pedal sound to follow an arpeggiator pattern (again, this is best programmed via the software editor). Where necessary, you can arrange to send any CC message on/off commands via the hold pedal. Layering mode allows you to choose a second patch as a layer sound so that when you press the hold pedal, the second sound is layered on top of your existing sound. Of course, sometimes you just want the pedal to behave as a normal hold pedal to sustain notes, and it can do that too. One mode I couldn't find (which I find useful on my Roland GR33 guitar synth), is the ability to hold only those strings currently sounding and to continue playing on the remaining strings.

Yet another new feature is that the AX100 MkII now has a drum sequencer on board. This can store up to 32 patterns that may then be combined in any of eight 'tracks' where each track can contain up to 32 pattern steps. This is very much like programming a traditional drum machine, and could be useful both for rehearsal and performance. In the Global menu, you can now set default individual values for each CC message and there are also two separate assignable pedal inputs that let you generate separate CC messages by plugging in the optional VP26 Swell pedals.

In Use

The hardware reminds me somewhat of an old Emu Proteus synth with its two-line LCD window and clearly marked round buttons. A socket for the GK pickup cable resides to the left of the panel after which is a variable level headphone outlet and an adaptor is supplied that allows the use of phones fitted with a 3.5mm mini-jack. A dedicated knob is used for display contrast adjustment, which is better than fishing around in menus, while the rest of the buttons are grouped to the right of the display. Six of the buttons relate to function (Global, Utility, Chain, Preset, Store and Edit) with the remaining four providing parameter and value up/down buttons for navigation and parameter editing. Though this device has a lot going on inside it, it is actually very easy to understand and program, but as with most menu-driven systems, it is faster to use the software editor if you can.

The rear panel of the AX100 MkII has MIDI In, Out and Thru connectors as well as a socket for the hold switch and two further sockets for the optional expression pedals. A further switch allows the user to step through a previously arranged chain of presets for live performance and there's also an output for the normal guitar signal, plus stereo jack outputs from the built-in soundcard. Power comes from a 12V adaptor, which I always find frustrating on equipment designed for live performance.

If you try to play the unit without first setting the string sensitivities, the results are likely to be less than impressive, so it is worth taking a few minutes to get this right. I used an electric guitar fitted with a Roland GK2A pickup and found that there was plenty of adjustment range available from the setup parameters. Perhaps the most important adjustment is the balancing of the individual string sensitivities, as it is impossible to play evenly until this has been done. One frustrating thing is that you have to manually switch to the string you wish to adjust — my Roland GR33 system does this automatically whenever you pick a new string. Again, using the on-screen sliders in the software is a much faster way of working.

After looking at the simple front panel, the rear offers a few surprises. Apart from the standard MIDI trio and four different connectors for pedals (two for the continuous expression type and two for Chain and Hold footswitches), separate stereo outputs are offered from the built-in soundcard, and there's a single output that allows you to take the raw guitar output elsewhere for further processing.Photo: Mike CameronWhen you come to play, the technique is different depending on whether the patch is set up for chromatic operation or to follow pitch bending. You also need to remember which hold pedal mode relates to the preset you're playing. There's no doubt that the Axon is extremely fast at note recognition and even with the piano sounds I couldn't hear or feel any delay, not even on the low notes. However the system is less good at following trills, as it seems to have difficulty identifying very fast consecutive pick strokes on the same string. You also need to play very cleanly, and it took me a little while to adapt my playing style, as I normally hold my pick very close to the end so that I can strike harmonics with the side of my thumb. This playing style is not appreciated by the AX100 MkII, as any finger contact with the string is likely to send it off tracking a harmonic, so I found it best to hold the pick around halfway down and to play as cleanly as possible. It is also vitally important that the guitar doesn't suffer buzzes at the bridge or on the frets as this can lead to erratic triggering, so it can pay to use slightly heavier strings than you might normally, and not to set the action too low.

All the pitch-tracking guitar synths I've used to date can give problems by retriggering when you lift your finger off a string, but the Axon's ability to adjust the triggering threshold helps keep this to a minimum, as does palm-damping the strings after playing a chord. Where the sound has a long release time, the pitch remains true during the decay period, even when you damp the strings, which isn't something that can be said of all MIDI guitar systems. When changing chords, it can also help to use the hold pedal to freeze out any accidental retriggers during the changes, especially if (like me) you're not the cleanest of players. As you might expect, percussive sounds such as acoustic piano are the least forgiving of sloppy playing, while pads, especially those with slower attack times, will let you get away with almost anything.

The built-in soundcard provides a perfectly competent GM sound set, but it isn't particularly exciting, and the outputs are a hint on the noisy side for serious recording use. In my opinion, you'd be better off using the AX100 MkII with external MIDI modules or software synths, but first you have to remember that if you want to use pitch bend, you'll need to set up the sound source to receive on six MIDI channels and also set the pitch bend range to match that of the Axon (usually a value of 12 semitones works well). If you don't need pitch bend, or only use it when playing monophonic lines, then you can leave the sound source set to Poly mode as normal.

Where the AX100 MkII seems to really score over rival systems is that external sound sources behave just as well as the internal ones. Both are triggered via MIDI, so that's to be expected, but with some systems, the internal sound-triggering bypasses MIDI completely and when you try to control external MIDI sound sources, the results are less impressive than when using only the internal sounds.

The ability to set up different zones, not only by string but also by picking position, works extremely well and opens up a lot of creative possibilities. The same is true of those hold modes that allow you to switch or layer sounds. I also like the way that string position can be mapped to controller value so that you can control filter settings and suchlike in a progressive way by moving along the string as you play.

Conclusions

While the AX100 MkII embodies some extremely clever technology, you still have to clean up your playing to get the best out of it, especially when playing piano-like sounds with percussive attacks, but it tracks extremely quickly and does a great job at controlling external MIDI sound sources and soft synths. There are various playing techniques that can be adopted to make playing a more positive experience and most can be picked up fairly quickly. Factors like your choice of string and the pick you use also make a difference, and I found that a smooth, medium-thickness pick worked as well as anything. Some guitar synth players also like to put a felt damping strip under the strings next to the nut to stop open strings from resonating, but this of course means not using open strings, except to trigger short notes.

For the recording guitarist who isn't comfortable with keyboards, the AX100 MkII can't be bettered for use with a sequencer, and although you invariably end up with a few spurious short, low-velocity notes where they shouldn't be, they're usually easy enough to remove if they cause problems. We still haven't got to the stage where we can completely ignore the technology and just carry on playing as normal, but the AX100 MkII brings that goal a little closer. I really appreciate the way this version of the Axon system works just as well at controlling external MIDI sounds as it does triggering its own sounds, and the positional sensing features are a great aid to making performances more interesting. As I said in the introduction, the search for the perfect guitar controller is far from over, but this new model from Terratec Producer brings it at least one step closer.