Yamaha Motif Rack XS

Photo: Mike Cameron

Yamaha's Motif range has proved to be both popular and enduring - so is the latest incarnation, the Rack XS, your cue to join the Motif party?

The chances of seeing one of Yamaha's Motif instruments amongst a band's line-up are fairly high these days, which can be taken as an indication of their deserved popularity. The range has moved on apace since the release of the first generation of Motif keyboard workstations in 2001. Since then we've seen the Motif Rack, Motif ES keyboards, Motif Rack ES, MO6 and MO8 keyboards and, most recently, the Motif XS keyboards.

It took a year or more for the first two generations of Motif keyboards to be followed by their rack-mounted equivalents, and the new Motif Rack XS is no exception — the XS keyboards from which it is derived have been around for almost exactly one year. It's a steady product history, and one that has seen a number of revisions along the way.

Previously, On XS-enders...

The arrival of the XS keyboards heralded some significant changes, particularly to the Motif's synthesis engine itself. Firstly, the instruments were kitted out with a new and more powerful SWP51 tone generator, as well as a newly developed wave ROM. Prior to the XS range, all Motifs used the same basic AWM2 engine: a Motif 'voice' was constructed of up to four layered Elements, each one essentially an independent synth using sampled waveforms as 'oscillators' — an architecture typically found in many other 'Sample & Synthesis' instruments. However, the XS raised the bar by doubling the number of voice Elements to eight, and implemented a new feature called XA, or Expanded Articulation. This takes advantage of the four additional Elements to give the player access to alternative instrumental articulations, not unlike the key-switchable layers offered by software samplers, allowing for greater expression and realism.

The onboard effects also received a make-over, which included the addition of several modelled 'vintage' effects, while the number of preset arpeggiator patterns increased to a whopping 6633. The XS keyboards also provide the means to create your own arpeggios. At this point, the XS keyboards and Rack XS part company, as the keyboards go on to include further features not included in this rack version. The most obvious missing feature is any form of sampling or importing of waveforms — indeed, no method of sound expansion is possible. Like the XS keyboards, the Rack XS offers no compatibility with Yamaha's range of PLG expansion boards, relying on the internal wave ROM to provide all of its raw material. There is no onboard sequencer, either — but this comes as no surprise on a module which would almost certainly be used with some sort of DAW sequencing software. So while the Rack XS could not be described as 'the Motif XS in a box' in a totally literal sense, the most significant aspects of the XS — its synth engine, effects and preset arpeggios — are all here. (Note that since the Rack XS has no audio inputs, the Vocoder Insert effect from the XS keyboards is not included, for obvious reasons.)

Rack XS Architecture

The Rack XS has two primary modes of operation: Voice Mode, which plays single voices on the basic MIDI channel, and Multi Mode, which is used for 16-Part multitimbral sequencer performances. Multi Mode is also capable of another method of operation, equivalent to what the XS keyboards call Performance Mode, in which the first four Parts of a Multi all receive on MIDI channel 1. The mode is used for those multi-layered, arpeggio-driven soundscapes for which the Motifs are famous. The switch to put the Rack XS into Performance Mode (called 'Layer 1-4 Parts') can be found in the Utility/General menu, although it would perhaps have been more convenient to have a front-panel control.

The effects also form an important part of the voice architecture: in Voice Mode, each Preset has (in order of signal flow) a two-band EQ for each Element, two Insert Effects, a three-band EQ, two System Effects (named Chorus and Reverb, although the Chorus slot can contain other types of effect), Master Effects and, finally, at the end of the signal chain, Master EQ. That little lot is going to have a substantial influence on the sound!

In Multi Mode, the deployment of effects needs to be more carefully considered. Insert Effects can be used on up to eight different Parts, while all 16 Parts enjoy their own independent EQs. The System Effects, Master Effects and Master EQ are placed globally across the main stereo output, so should be chosen to suit the total mix. In the case of the Master Effects and EQ, these can be bypassed altogether if not required.

There are two other notable improvements over the Motif ES rack: firstly, Drum Parts can now be edited in detail from within a Multi, meaning that if you want to edit any single drum sound — filter it, change its envelope, add reverb or send it through the Insert Effects — you can. Secondly, a Part's Insert Effects can be freely changed from within a Multi without the need to return to Voice mode, choose new Insert Effects for that particular Preset, and re-save it as a new version. Note that both of these functions are only available when using the Rack XS software editor.

The Hardware

The Rack XS's front-panel design is a radical departure from previous Motif rack models. Firstly, the buttons have been redesigned, reorganised and reduced in number. Four dedicated cursor buttons provide navigation through an easy-to-follow menu system, and a detented knob adjacent to the LCD display is used to scroll through presets — pushing this knob inwards brings up a category search window to help you zero in on the required sound. The output volume knob and on/off switch have been combined into one, and turning the knob fully anti-clockwise until it clicks kills the power. This could be inconvenient if you've set the volume knob at a critical position — you might want to power off at the mains socket instead if you don't want this position to be altered!

The rear panel of the Rack XS features a PSU input socket, a pair of stereo outputs and two assignable outputs, S/PDIF output, MIDI In and Out, a USB port and an expansion slot for an optional mLAN board, should you need additional outputs.Photo: Mike Cameron

The most interesting change, though, are the five new rotary encoder knobs at the right of the panel. While you might expect most of the hardware controls of the keyboard version to be absent on its rack equivalent, Yamaha have managed to incorporate some of these real-time controls in the Rack XS. These knobs control 20 different functions, as the adjacent Select button cycles through four different rows of possibilities, listed above each knob. Eighteen of these functions are fixed, while knobs 3 and 4 in the fourth row can be freely assigned to the parameters of your choice. These knobs might be of limited use if they did not transmit their data over MIDI, but happily they do, which will be of tremendous help for anyone who doesn't own a hardware control surface.

The parameters chosen for these knobs generally operate at the Common Part level — which is to say that they apply offsets to the overall sound. Bear in mind that if a certain parameter is not applicable to a sound (for instance, if all its Elements' filters are set to 'off'), turning the Cutoff or Resonance knobs will have no effect! When you're working with the Rack XS in Multi mode, simply use the left/right cursor buttons to select the Part you wish to tweak. The functions of the knobs will then be redirected to that Part, and their movements can be recorded onto the appropriate MIDI track in your sequencer.

Connections on the rear panel also differ from previous models. Firstly, there are fewer audio outputs than before — two main stereo outs, but only two assignable outputs instead of four. This is an understandable economy, given that an optional mLAN board can be installed if more outputs are required. (See the 'Software Support & mLAN' box.) The remaining connections are a DC input socket (for the supplied external PSU), MIDI In and Out (but no Thru), S/PDIF out (but no optical out) and a USB connector — essential for using the Rack XS with its excellent software editor.

The Road Of XS

The XS keyboards saw Motif synths mature into versatile and expressive instruments, equally at home on stage or in computer-based studio setups. The Rack XS brings all the synthesis power of those instruments to a compact 1U rack module, but without the sampling and sequencing facilities. Many users will find that the factory Presets, which cover a wide range of musical genres, fulfil their needs and require only minimal surface tweaking. Sound designers and inveterate dabblers, on the other hand, will find that the Rack XS Editor is invaluable (indeed essential) for getting to all the deeper-level parameters that cannot be accessed from the front panel.

To sum up, if you've already got all your sequencing, sampling and audio needs covered by your DAW program, the Rack XS is an ideal way to add Motif XS sounds to your sonic armoury.