Even a relatively modest MIDI setup can create MIDI routing problems, and solutions to these aren't always easy to find. Paul Ireson investigates the range of Philip Rees MIDI management boxes to see what they can offer.

Whilst the introduction of computers and MIDI into the world of music has saved keyboard players from having to grow extra arms and fingers in order to control their Wakeman-esque banks of synths, it has in turn created new control problems: how to manage the MIDI data streams cruising around those ubiquitous DIN cables. The basic problems are those of switching MIDI data between different pieces of equipment, and merging and distributing data. Major manufacturers are only too happy to produce more and more pieces of equipment that generate and consume data, but when it comes down to producing anything to physically manage MIDI connections, they don't seem very helpful. Fortunately, a small British company, Philip Rees (Modern Music Technology), produces a range of boxes that fill precisely this role, and solve all of the common MIDI interconnection problems: the V3 and V10 MIDI Thru boxes, the 5S MIDI Switcher, the W5 Dual Input Thru box, the 5X5 Switcher, and the 2M MIDI Merger.

PROBLEMS, PROBLEMS

The first connection problem most MIDI users encounter is simply running out of MIDI Out sockets to drive MIDI Ins. Let's imagine you have a computer running a sequencer program, a synthesizer, a drum machine and two synth expanders. When playing back sequences in which everything is slaved to the computer, there are four hungry MIDI Ins waiting to be fed by the computer's single MIDI Out (assuming you are using an Atari ST, or a computer whose MIDI interface has only one MIDI Out). One way to distribute the MIDI data is to join the various devices together by a chain of MIDI Thru connections, where each subsequent MIDI In is fed from the MIDI Thru of the previous device. However, even if all of your gear incorporates Thru sockets (many older units do not), such a chain can create timing problems. These arise out of the fact that whenever MIDI data is echoed from the In to the Thru socket of any piece of equipment, a very slight time delay is introduced. By the end of a chain of Thru connections, the accumulated delay will be sufficient to noticeably affect the timing of percussive parts relative to that of instruments at the start.

The alternative to a 'chain' connection is a 'star' network - splitting the single MIDI output into several identical streams, each of which can be sent direct to each slave instrument's MIDI In. Unfortunately this is not simply a matter of soldering together a special lead, as a single MIDI Out or Thru connection does not have the power to drive more than one MIDI In. What you need is a MIDI Thru box that accepts a single MIDI input and produces several identical MIDI Thrus, and Philip Rees produces two such units - the V3 (three Thru sockets) and V10 (10 Thru sockets).

V3 AND V10 THRU BOXES

The V3 could well be the smallest device in your MIDI setup - it's about the size of two 9-volt PP3 batteries, with the four sockets (one In and three Thrus) mounted on the top of the case. The V3 can be powered by a single PP3 battery (which should last several months in normal use), although it can also be run off a mains adaptor.

The V10 takes the form of a slightly larger block, with the 10 Thru sockets arranged along the two long edges. Like all other Philip Rees boxes (apart from the V3 and unpowered 5S) the V10 is mains powered, with an internal transformer, captive mains lead and ready-fitted plug. Both the V3 and V10 are simple, straightforward and work perfectly, and that's all there is to say about them.

5S MIDI SWITCHER

The next problem that most people encounter is more or less the reverse of the first - how to assign one of several sources to a single destination. This is necessary, for example, when using a computer to edit sounds on synthesizers and expanders. Although a star network will allow the computer to address all of the synthesizers' MIDI Ins, the MIDI Out from each synth must also be connected to the computer's MIDI In socket in order for it to be edited.

This means that a serious editing session requires a lot of lead switching to connect each synth in turn to the computer's MIDI In. The Philip Rees solution to this problem is the 5S MIDI Switcher: a small, unpowered unit about four inches square and two inches deep, with a single MIDI socket on the left edge and five on the right. A rotary switch on top of the unit connects the single socket to any one of the other five, and there is a blank 'scribble space' by each switch position which allows you to write down in chinagraph pencil what equipment is connected to the 5S. I deliberately haven't described the sockets as being In, Out or Thru, because the MIDI data can flow through the 5S in either direction. You can therefore use the 5S as a selector box either to route a single source to any one of five destinations, or to select one of five sources to address a single destination.

W5 DUAL INPUT THRU BOX

A Thru box or switcher is quite adequate when there is only a single source of MIDI data, but if more than one source is required you may once again find yourself having to re-plug a set of MIDI leads. The two sources might be a master keyboard and a music computer, or two separate keyboards - some people do still play more than one keyboard at once. A useful device to deal with routing here is the W5 dual input Thru box, which allows five outputs to select either of two inputs as their sources. Switching is carried out by means of five three-position sliding switches (A, B and Off) located in line with each of the five Thru sockets down the right-hand edge of the box. Scribble space allows you to indicate what is connected to each In and Thru. The switches are a little hard to see from a distance, but nevertheless provide an immediate indication of how signals are routed.

It is interesting that all the routing in Philip Rees boxes is carried out by hardware rather than software-controlled switches - interesting because the world of MIDI is inhabited by digital rather than analogue signals. Whilst avoiding software means that none of the boxes are programmable, it brings the great benefit of ensuring a constant, reliable indication of what is going on at that point in the MIDI chain.

When engrossed in MIDI, even the most ardent technophile has moments of data-induced despair, as he/she tries desperately to work out just why something that should be sounding isn't, or why that module that shouldn't be beeping is. The reasons for such unexpected occurrences are usually buried a couple of steps into the operating routines of the instruments, but with the Philip Rees units you can glance at them and know that you have a reliable indication of what's going on.

I suggested earlier that the W5 is useful wherever two controllers are used in a setup: this could be two keyboards or a computer and a keyboard: but more and more these days, it could be a single computer. Several sequencer programs now support multiple sets of 16 MIDI channels (Creator/Notator, Trackman, etc).

With two sets of 16 MIDI channels emerging from your computer, a Thru box with a single MIDI In is no longer sufficient - the W5 is thus ideal for deciding which of two sets of 16 channels each of your multitimbral expanders is tied into.

2M MIDI MERGER

Further problems are associated with merging MIDI data streams: for example, when you want to record two MIDI instruments 'live' into a sequencer, or when two controllers (keyboard and guitar synth perhaps?) need to control the same multitimbral expander. Theoretically, it would be possible to simply solder a couple of wires together to give two Outs simultaneous access to a single In - but data streams don't take kindly to this kind of treatment. If only one of the sources is transmitting at any one time, its data will arrive without any hitches; but simultaneous transmissions cannot be dealt with - bytes arriving at the same time will be corrupted, and the resultant garble will be unintelligible to the receiving MIDI unit. The practical implications are that Note-On, Note-Off, Program Change and other messages might not be received, which could seriously affect a performance.

What is needed here is an intelligent MIDI merger - one that thinks about what it is going to do with the data streams before combining them. Not surprisingly, there is a Philip Rees unit that does just this: the 2M MIDI Merger.

The 2M comes in the same size box as the 5S and W5. Down the left-hand edge of the case are two MIDI Ins, and there are two Thrus and two Outs on the right. Each Thru echoes the data received at one of the two Ins, and the two Outs provide identical merged outputs. In use, the 2M interleaves data bytes from the two sources so that none are lost, and gives priority to clock data so that the timing of music remains unaffected. In fact, it is not always possible to ensure that no bytes are lost: if one of the sources pumps out data at the full MIDI rate - by transmitting a System Exclusive dump, for example - there simply isn't room for any more data to be added to it, so something has to give, and data will be lost.

An interesting point about the 2M's merging capabilities is in the way that it combines Pitch Bend data - two streams of Pitch Bend data on the same MIDI channel will be arithmetically combined, rather than merged with interleaved bytes which could cause the slave unit's pitch to jump up and down rather erratically. In practice, things work like this: if the sensitivity of the receiving expander is set to produce a wholetone bend at full range, and one bender lever is pushed half-way up, a semitone bend up is produced. Movements of the second bender lever will then produce variations around this pitch, so a slight tweak up will raise the pitch of the note just a little more, and releasing the second lever will take the pitch back to one semitone up.

5X5 MIDI SWITCHER

Perhaps the most versatile of the Philip Rees boxes is the 5X5 MIDI Switcher, which is effectively a five-input, five-output MIDI patchbay. Each of the five rear panel Outs can be fed by one or more of the five Ins (or set to Off, so that no signal is routed to it). The 5X5 can therefore function either as a flexible Thru unit to distribute signals, a simple patchbay, or a kind of 'dumb' merger. The routing is carried out by five six-position rotary switches on the front panel of the 5X5 - there are scribble spaces on the left of the panel to jot down what units are connected to the Ins, and below each switch to write down Out connections.

I describe the kind of merging that the 5X5 carries out as 'dumb' merging because it runs into the problems that the 2M avoids - as outlined above, data bytes that arrive simultaneously on merged data streams will be corrupted. However, this does not really matter for the most common merging application, which is that of connecting a master keyboard and a computer to an expander at the same time, so that sounds can be played as they are edited. In this case data does not have to arrive simultaneously from both sources, so the 5X5 is quite adequate - and when you've finished editing your expander's sounds and want to start using your sequencer again, the master keyboard's output can be routed to your computer's MIDI In at literally the flick of a wrist.

If five MIDI Outs isn't enough for you, X5X expander units can be linked to the 5X5 to provide a five-In, 10-Out (or even 15-Out) MIDI routing system.

The flexible nature of its routing facilities make the 5X5 the ideal heart of a MIDI management system: a computer and master keyboard generate all of the data, but something else is required to deal with the physical side of routing MIDI signals. The 5X5 allows your equipment to be easily reconfigured as different applications require.

CONCLUSION

Anyone with more than a couple of pieces of MIDI hardware will inevitably have found themselves groping around the back of various pieces of equipment in the process of re-routing MIDI cables. This is at best a frustrating business, and is often one of the major obstacles to using your equipment to its full extent. The various Philip Rees boxes offer solutions to all of the common MIDI routing problems-switching, merging, and distribution - and offer the solutions in a straightforward, intuitive manner. Each of the units solve particular problems, work perfectly (each unit comes with a three year parts and labour guarantee!), are good value, and fill a particular niche that no-one else seems to address. On the strength of these boxes, Philip Rees is my nominee for the MIDI world's Red Adair trouble-shooting prize.

FURTHER INFORMATION

V3 £12.95 (mains adaptor £6.95 extra), V10 £35.95, W5 £49.95, 5S £25.95, 5X5 £89.95 (X5X expander £79.95), 2M £79.95.

Philip Rees (Modern Music Technology), (Contact Details).