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Yamaha MU90R

GM/XG Tone Generator By Christopher Holder
Published May 1997

Yamaha have scooped the insides out of their well‑specified MU80 half‑rack GM/XG sound module and transplanted them into a full rack case, with a few extra features aimed at making the resulting MU90R stand out from the GM crowd. Christopher Holder is generally impressed...

I'd hazard a guess that there are very few people who are composing and playing back nothing but GM, GS or XG files. So for most people these days there's got to be more to a sound module than General MIDI and its variants — an angle, something that will make even the severest GM critic say "yeah, it's a GM module — but take a look what else it can do". Roland's Sound Canvas dynasty persists, with the new Sound Canvas Pro offering more than before; Korg weighed in with the NS5R, offering GM, GS and XG compatibility, as well as heaps of other sounds and a idiot‑proof user interface; now Yamaha have decided that their GM line might benefit from some tinkering under the bonnet. What they've come up with is an MU80 in a 19‑inch rack unit, with more of all the things that made the original module outstanding two years ago.

Extra, Extra!

If you don't already own a MU80 and are unfamiliar with it, before going further with the review in hand I should direct you towards our April 1995 issue for a full review. If you haven't got that copy, or you're simply bone idle, read on nevertheless. In short, the MU80 gave you everything you'd expect from a GM module and a bit more — more sounds (via Yamaha's XG protocol), 32‑part multitimbrality, 64‑note polyphony, a performance section with lots of big, impressive sounds, a powerful effects section and, notably, an A/D input which can be routed through the effects and mixed out of the stereo outputs.

But, to coin a completely throwaway line, that was then and this is now. What's most obvious at first glance is that the MU90R has been built into a full 19‑inch rackmount chassis rather than the half‑rack box that the earlier MU80 (and its lower spec'd little brother, the MU50) inhabited. I think this is more of a physical necessity to accommodate the extra bells and whistles on the front panel than it is a shift in market emphasis by Yamaha — although it's true to say that GM multimedia music makers are far less likely to be packing a rack unit. The LCD remains the same in its dimensions and default multi‑mode information content. All the buttons for editing and navigating around the machine remain the same, as do the volume knob and phones socket. What's new about the MU90R, bringing it to full‑rack‑width status, is a data dial, an extra A/D input, and a chunkier, more industrially specified power switch. A glance around the back sees the welcome inclusion of two extra individual outputs on top of the existing stereo outputs.

The improvements don't stop there. Inside there's more of everything — more sounds (779 voices, 200 performance programs), more effect types and more drum kits (30 in all). The MU90R operates in four modes: XG, TG300, C/M (GM) compatible, and the unit's own Performance mode. Digging through the various banks and voices, with a little work, you can unearth some classy sounds. The strings are generally tip‑top (including the 'synth' strings and pizzicato varieties), there are some big analogue synth leads which are great for instant '80s killer riffs, some of the synth basses span the subsonic to the brash (often within the same patch), and I have to reluctantly admit that even a few of the wind instruments are quite pleasing to my ears — but, of course, the nature of General MIDI‑based synths dictates that you're bound to be wading through chamber orchestras of bassoons and French horns when all you want is to hear is more of those great swirling pads and brash polysynth samples. Happily there aren't any true shockers in the Yamaha palette of sounds, although the pianos wouldn't be my first choice (nothing about the sound quality seems velocity sensitive other than the volume) and the bagpipes still curdle my Famous Grouse.

In Performance mode the MU90R boasts 200 programs (100 each in ROM and RAM), each combining up to four normal voices at a time. This is not a multitimbral mode and is intended for solo performance. The calibre of sound here takes a quantum leap and is redolent of a box considerably more pricey than the MU90R's £599 asking price. Washy, evolving pads, thick analogue leads and chunky organs are in bountiful supply, as are some hilarious dance/rave effects. There's something about the Yamaha sound that miraculously combines both the thick and the transparent, which is great when you're trying to shoehorn one of these patches into an already‑busy mix. If you're out of the studio and taking the MU90R on stage, many of the sounds are quite responsive to velocity, while assigning the filter to your mod wheel produces some beautifully smooth sweeps. There's a good level of editing and sound‑creating potential here, with individual control over each of the four composite voices, including individual effects levels. You only wish this mode could be made multitimbral — after all, the Korg NS5R managed this with its Combination mode.

Proof Of The Pudding

To see how the MU90R performed in a real‑life situation, I set off on a one‑hour voyage of compositional discovery. Strings, synth bass, piano, drums, polysynth stabs and lots of incidental bits of wibbly flotsam and jetsam took shape before my better half even realised where I'd disappeared to. Control over main levels, reverb and chorus levels and panning is all there before your eyes for instant tweaking, and I was pleased to hear how quickly each component in the mix found its own space. There's plenty of variety in the drums and percussion too. After appreciating all the various bass drum options, I had to settle on a 'Techno Kick' (combines all the best elements of the 808 and 909 kick) and a Caribbean boatload of sizzling percussive effects. I couldn't resist routing a 909 hi‑hat pattern from my Roland R8 MkII drum machine into the A/D input and then grunging it with a distortion insert effect, and a bit of phaser from the Variation system effect. The result, although not high art or a cutting‑edge floor filler, was something that encouraged me enough to work on the track further with my other sound sources.

Feature Presentation

The MU90R's downsides are hardly critical, but are worth mentioning. I think the buttons on the front panel could be a little more finger‑friendly and a little less fiddly, and I wish there were least a couple of memory locations to store multi mode setups (as it is, you're forced to use SysEx to dump your setups, via a SysEx dump page that sports a dump truck icon to add further spice to the hilarity that is system exclusive). Another change to make life easier would be an additional multi mode occupied by the complete soundset in bog‑standard, sound module banks of 128 programs. This would give the GM/XG option to those who want it and an alternative sound module operation for the remainder. I can't believe this would significantly add to the MU90R's cost.

There are other GM modules out there with more sounds, more sophisticated editing, and more sound‑creating power, but these aren't the MU90R's selling points. What makes the MU90R special are the two A/D inputs, which add loads of possibilities to your songwriting and your on‑stage performance, and the effects section, which is very impressive. The data wheel speeds up operations tremendously, while the two extra outputs are most welcome. Like the previous models, the MU90R can also act as a MIDI interface, and can be plugged directly into your Mac or PC's serial port.

In short, this is is a very reasonably priced, reasonably friendly songwriting tool that offers another interesting slant on the General MIDI module format. Working with the MU90R is dead easy and if you're looking for one unit that you can rely on for trying out your ideas, it's perfect.

Just For Effect

Along with the two A/D inputs, the MU90R's effects section is the outstanding feature of this machine and is significantly more sophisticated and flexible than anything else in its class. What's on offer is an impressive three system effects, supplemented by two assignable insert effects, and a digital EQ across the mix buss for good measure.

The system effects include Reverb, Chorus, and Variation. Twelve reverb types are on offer, ranging from the Basement simulation, with a reverb time of 0.6 seconds, to the unlikely ambience of a canyon, with a reverb time of 12 seconds. The general idea for the operator is to select one of the 12 reverb programs and enjoy the fruits without any twiddling required. Although impressive, the presets are tad bright for my taste, which is generally easily remedied with a flick of the LPF setting, while bringing down the default Diffusion setting gives the reverbs the density I prefer. A notable omission is a Spring Reverb program.

Next up is the Chorus section, where you'll find 15 spatially expanding and tone‑thickening effects. All the default settings are rather demure for my liking and need some tweaking. The phaser is nicely dynamic, the flangers (described in the manual as 'reminiscent of a jet airplane') are useful but not gee‑whiz enough, or appreciably different enough to warrant the three on offer. The section has a Chorus into Reverb send control which adds further flexibility.

The Variation effect control on the 'home page' is a switch, with a wet/dry mix setting on the Effect Edit page. As well as all the chorusing and reverb options you have the full palette of distortions, speaker simulations, EQs and non‑linear reverbs. The guitar effects deserve a special mention. Amp simulations, wah‑wah effects and overdrive all work rather nicely on the guitar patches, but can also be pressed into service for various other tasks, working on analogue synth patches, drum parts, or vocals from the A/D input — great for creating White Town vocals and Chemical Brothers grunge.

There are two Insert effects that can be assigned to any two of the 34 parts (including the A/D parts); any of the effects are available for this. If you want more flexibility, how about being able to change the Variation effect into a third Insert effect, which is done from within the Variation effect edit pages? The applications for Insert effects are as obvious as they are useful — distortion for your guitar (a synthesized one or a real one plumbed into the A/D input), a rotary speaker for your organ sound, a compressor for your vocals — the list goes on.

As mentioned, the effects are designed to swing into action without any editing, and the number of parameters on offer don't give you supreme control — but you wouldn't expect it from a unit such as this. I can remember many times when I've tinkered with effects patches and come up with something so mind‑blowing, so bizarre and dynamic that it kept me amused for hours, but then had to sacrifice the extraordinary for the mundane necessity of the Small Hall patch. The number of options available on the MU90R should help to do away with that sort of frustrating situation. I've always considered effects programming to be a synthesis technique in itself, especially in the realms of Techno, where a wisely tweaked effect on a sound might just give it the freshness it needs to stand out from the preset crowd.


  • Classy and versatile effects section.
  • Two additional outputs.
  • Good manual with glossary.
  • Two A/D inputs.


  • Normal voices sometimes drab or shrill.
  • Interface a bit fiddly.


With these features, and at this price, the MU90R deserves consideration from multimedia musicians, project studio owners and live musicians alike.