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Dr.T Xor

System Exclusive Orchestrator

If you have a large number of disorganised patches and an unruly MIDI network, then Xor is made for you. It is designed to make sound management and working with MIDI instruments easier. Martin Russ finds out if the claims are true.

It is probably fair to say that Xor is very nearly exactly what everyone has wanted ever since MIDI was first unleashed upon an unsuspecting music industry - something which frees you from worrying about the nuts and bolts of producing and storing sounds and lets you concentrate on using them for making music. Unfortunately, as anyone who has been following my 'System Exclusive' series in this magazine will already know, the reality of using sounds can often get really complicated when large numbers of them need to be stored and recalled.

Universal librarian programs, like Hybrid Arts' GenPatch ST, go some way towards what is needed, but they are not very good at recalling patches 'stacked up' from several instruments, or from everything in a typical MIDI system. Trying to tie effects units and sound patches together is fine on an integrated workstation like the Korg M1, but is trouble-prone with two separate devices. Xor finally brings complete integration to patches, setups and performances, and aims to make your entire MIDI network behave like one single instrument. So is it a potentially indispensable tool?


Xor is the second program I have looked at recently which requires you spend time with it before it can be used effectively. This seems to be a result of the way that MIDI software has evolved in the increasingly complex hi-tech world. RealTime from Intelligent Music works best if it is told the channels of the synthesizers and drum machines which it is driving, because it then lets you use these device definitions to automatically configure a track - no need to change MIDI channels ever again! Xor takes this configuration idea several stages further. In fact, you need to prepare Xor so that it is suitable for your equipment before anything will work.

To begin with you need to prepare a working disk containing the appropriate Xor program files, together with the profile files which match your equipment. A 'profile' is a definition of the System Exclusive and editing features of a particular device, and these are used to configure Xor so that it provides the right support for each individual instrument. There are currently over 40 pre-configured profiles available from Dr. T, and these cover the majority of popular instruments and effects units, with more being programmed by Dr. T all the time. Eor, the Xor profile editor program, is expected to be released in the near future and will enable any user to define their own profiles, although Dr. T do stress that this is not for the casual user. Those of you who have been following my 'System Exclusive' series should not be deterred!

This working disk is the one you will normally use, although the copy protection scheme means that you will need the original disk as a 'key' when you start each session with Xor. Because of the large number of sound patch files which can accumulate, Xor is designed to take advantage of the storage and speed of a hard disk drive - Dr. T suggest creating a separate folder for each synthesizer, to store your patches and performance data.

Once the working disk is ready, the final stage of preparation is to teach Xor about your system; so far the working disk contains profiles for each instrument you have, but no details about the MIDI channels they occupy. The Setup Editor program is used to teach Xor about how you have configured your system, especially any MIDI patchbay you might be using.


A significant amount of Xor's power comes from the way it manages your MIDI network, especially the switching of MIDI data between instruments and the computer. Here Dr. T really encourage the purchase of a MIDI Patchbay or Switcher unit for the serious user, because it enables you to wire up the network once and then forget about it - Xor will control the patchbay so that the appropriate instrument is connected to the computer at the right time. This is the missing link between patchbays and patch librarians: although most MIDI patchbay owners have programmed them to select specific instruments for particular MIDI Program Change numbers, few librarian programs can send the necessary Program Change messages. When you use the Setup Editor, you tell Xor about how you have configured your patchbay. Once it knows, you can almost forget that the patchbay is there!

The working disk is prepared, and the Setup Editor has been told how your network works; so unless you add more equipment, the hard work is over. Running Xor loads the files which configure it to work with the equipment you have described, so you get your own personalised system! As if to emphasise this aspect, the first thing Xor does is display a screen which you can use to store text remarks or reminders. After this, the Performance window opens...


Some people call them performances, some call them patches, and others call them setups; what Xor means by a 'performance' is all the information needed to set your MIDI network to a particular state, which includes all the sounds, effects and global settings - everything! To reinforce the importance of the Performance window, it cannot be closed, and it acts as the control centre for all your interaction with Xor. Initially, no performance will be available, and so the Get Performance menu option causes Xor to request a patch dump of the current sound or effect from each instrument or device in the network. With a patchbay this is automatic; without one, Xor reminds you to connect up the appropriate cables. (Dr. T place great stress on the benefits of MIDI patchbays in the Xor manual.)

It really is as simple as that - Xor now has a map of the current state of your entire system. You can Save or Load performances from disk, and Send a stored performance out to the network to restore it to a previous state. Probably the first thing you should do is to load all your stored sounds into Xor, and the bank functions are designed to make this easy as well. A 'bank' is a collection of patches or sounds which can be loaded into an instrument as a single group - the DX7, for example, can send its sounds in banks of 32 to Xor.


Banks can be stored as they are, and all the usual librarian type functions are supported, so you can move sounds from one bank to another quickly and create new banks for a particular song or set, and then save them. Individual sounds can be renamed by double-clicking on the name. Up to four banks can be open at the same time, but they must all be from the same instrument - Xor does not translate between synthesis methods! As with all operations in Xor, what you do on the screen is reflected in your MIDI network. So loading a bank causes the information to be sent to the relevant instrument. Similarly, selecting Send Performance transmits the sound patches to all the instruments.

Most ordinary librarian programs only provide bank type facilities; Xor adds another layer in the form of 'libraries'. Each instrument has its own library, which is used to store all the sounds or patches and enables them to be cross-referenced and easily retrieved. The first thing I did with Xor running was to transfer all my sounds into banks within Xor, and then to transfer the sounds into the library.


As you place each sound into the library, Xor asks you to classify it with some keywords so that you will be able to refer to it by name and by context. A wide range of keywords are provided, and Dr. T recommend using a keyword from at least two of the groups provided: 'Categories' covers types of sound (like 'synth', 'percussion', 'plucked string' etc), whilst 'Instruments' provides a list of instrument names. Other groups of keywords provide more descriptive terms: bright, soft, metallic etc, and an additional comment can also be stored for each entry. Each sound that you place into the library is also date and time stamped (assuming that you always set the correct time and date, or have a battery-backed clock for your Atari), so that a previously stored sound with the same name is not lost-although, in practice, a periodic clearing out and sorting through of stored sounds would help keep things tidy. Xor and its libraries will quickly become the focus of your MIDI network, so care and attention to detail will make it easy and efficient to use.

Retrieving a sound from a library file is merely a matter of defining the type of sound you want, using the keywords, or the name of the sound, or the additional comment. Xor's searching proved much faster and efficient than manually scouring through the bright, metallic sounds in the several thousand DX7 patches I have accumulated. You only have to mislay a favourite sound and then be unable to find it amongst your RAM cards or floppy disk files to appreciate why the effort of placing all your sounds into Xor libraries is time well spent! Once a sound has been found it can be placed in a bank, so that you can audition one or more sounds easily by sending the bank to the relevant instrument.

The important thing to remember about Xor is that once you have selected a sound from the Performance window, Xor will behave like a dedicated patch librarian for that instrument. Selecting another sound changes everything to reflect that instrument, so the library and banks will both change to show the sounds available for the newly selected instrument. Once you are used to this, most of the problems of using sounds with several instruments just melt away. You no longer have to think about running a separate program for each instrument, and you soon wonder why you ever bothered buying expensive RAM cartridges for storing sounds! Once you begin storing your sounds in libraries you soon find out why Dr. T recommend that you consider using a hard disk, and the ease of use which accompanies having all your voices available almost instantly makes the cost of an ST-compatible hard disk much easier to justify.


When you are assembling sounds into banks, or storing them in a library, there are certain utilities which some dedicated librarian programs provide, and Xor has three of the most useful: Blending or In-betweening, where you take two sounds and create a whole new bank of variations on them; Randomising, which takes a sound and varies the value of some of the parameters which define it; and Editing, which allows you to manipulate the most important parameters of the sound patches. As with everything in Xor, the editor is available for each instrument and is tied to the selected sound in the Performance window.

The Edit window opens when you select the Edit Patch option from the Edit menu (because of the complexity of most of the editing screens, it is usually best to click on the 'full' button in the top right-hand corner of the window to make the window fill the whole of the screen). The editing controls are made up of three main elements: sliders, text boxes, and graphs. All the sliders operate vertically, with a handle you can drag, or you may click above or below the slider handle for finer control. The text boxes are used to set On/Off and other text-based options, whilst the graphs are used to show (and edit) envelopes and pitch. Most of the editing controls are large, thus the screens tend to be large, so you will usually need to move around using the scroll bars at the left side and bottom of the window.

In common with the integrated aspect of everything which happens in Xor, editing a sound or patch works on the image held in the computer as well as the actual MIDI instrument. Storing a sound in the library does not replace the previous version, thanks to the unique date/time stamping, so you can edit sounds and place them in the library without any worries. Playing sounds whilst editing them has always been a minefield of potential problems for voice editing software, but Robert Melvin (the author of most of Dr. T's editing programs) was one of the first people to consistently use the right mouse button to play notes, with the screen mapped to low notes on the left, high notes on the right, and increasing velocity upwards. This method works remarkably well, and ought to become standard in all editing packages.

The editing controls work very well, the sliders have the right feel, and the 'nudge' option for moving them in single increments is extremely useful. Graphical envelope editors have always been popular with users, but because of Xor's generic nature, there seems to be less tailoring of the display to the way that the voice parameters actually work in the real instrument than you find in some dedicated editors. Still, the editor function really adds the icing to what is a very nicely made cake - even if you rarely use it, the editor is always ready and waiting in the background for when you call upon its services.


'Indispensable' is the first word that springs to mind here. The initial setting up process takes some time, and entering sounds into the library can be a lengthy process if you have large numbers involved, but the effort is repaid many times over when you start to use Xor seriously. If you don't use a MIDI patchbay, I must confess that the alert boxes reminding you to re-patch your equipment can quickly become tiresome, but if you are committed enough to use Xor and own three or four MIDI instruments, then a patchbay should be on your shopping list anyway!

I gradually became hooked on Xor. At first I just played around with swapping sounds and creating banks, but found myself becoming more and more dependent on being able to have virtually instant access to sounds, and trying to use those same sounds without Xor can be difficult. Once hooked, the withdrawal symptoms can be awkward: your set of 'available' sounds expands when you use Xor, and contracts frighteningly when you are not - few MIDI instruments give you immediate access to more than a hundred or so sounds, whereas with Xor and a hard disk, you can have all your synth sounds at your fingertips.

Running a sequencer like RealTime (my current favourite), which is not MPE-compatible, serves to remind you very forcefully that, without Xor, you really do have to work hard to keep track of where each sound is kept. In practice, I have been forced to load up sounds with Xor, then quit and run the sequencer. With the current fashion for multitasking using the ST (with Dr. T's MPE, Steinberg's MROS, C-Lab's SoftLink and Intelligent Music's ST-RAM, amongst others), I look forward to the time when all programs will work together towards a common goal. At this point in time, if you buy Xor, it works best in an MPE environment - so now could be as good a time as any to check out what MPE, KCS, and TIGER have to offer. (If any of these acronyms are unknown to you, please contact your local Dr. T dealer!)

Being a reviewer has its own particular man-traps. Instead of seeing a product for half an hour in a shop or reading reviews, you get to use the item for real for a few weeks and then it is taken away from you! (A popular myth is that reviewers get to keep everything they review! If only...) With some products the parting can be no problem, but for others the separation can be extremely painful. I simply had to buy RealTime for myself after reviewing it, and I feel the same about Xor - except that I don't presently make use of Dr. T's Multi Program Environment. So the question really boils down to this: Is Xor such a good product that you should buy it, and if so, do you need to commit yourself to an MPE environment? My dilemma is that it looks like the answer may be 'yes'!


£249 Inc VAT.

MCMXCIX, (Contact Details).


As of 8th September 1989, the list of MIDI devices supported by the Xor profiles is:

- ART Multiverb
- Casio CZ1/1000/3000/5000
- DigiTech DSP128
- Digital Music Corp MX8
- Ensoniq SQ80, ESQ1, ESQM
- J.L Cooper MSB+
- Kawai K1, K1r, K1m
- Korg M1
- Lexicon LXP1, PCM70
- Oberheim Matrix 6/12/1000, Xpander
- Roland D10/110/20/50/550, MT32, GM70, MKS70, R8
- Yamaha DX7, DX7II, TX7, TF1, TX216/816/81Z, SPX90II, DX100, DMP7, TX802

More instrument profiles are in the pipeline, and a Profile Editor is due soon.


Programs as complex as Xor can be a software support nightmare. A large number of supported instruments, hard disks and different patchbays, can all conspire to make achieving usable integration potentially difficult. In my case, the major problem was the patchbay. I am still using my own design of manual switch box, and so far I have found no commercial equivalent. Unfortunately, a MIDI patchbay/switching matrix box really is needed to fully appreciate Xor.

I am one of those people who hates throwing things away. This is why I still have my original DX7 (a very early model), my Pro-One monosynth (bought before Vince Clarke used one on 'Top Of The Pops') and a Kawai K5 (the bargain of the century, but that's another story). As a consequence, I don't have a rig which is anything like recent, and so Xor's profiles tend to be mostly for equipment I do not own. It seems to me that Xor will only succeed if it really can integrate your entire system, and for that it needs profiles for everything - and I mean everything.

Some of the documentation I received was sparse. The ring-bound A5 manual with its indexed 100 pages was fine, but the information about the profiles was different. For example, no matter how I tried, I could not get Xor to talk to my DX7 properly, and eventually I resorted to sending patches manually. The problem was that there was no guidance as to what I should have been doing! Luckily MCMXCIX, the UK distributors, seemed to have no problems getting Xor to work, so they should be able to sort out any enquiries.

I really didn't like the Caged Artist Editor's master sliders - those on the left-hand side of the window - that are used by clicking on a parameter and then moving the mouse vertically until it 'grabs' the slider handle. This is not employed in the Editor windows, but appears in the other windows.

Xor is copy-protected. The master disk acts as a 'key' disk which you need to have in the floppy drive when you first run the program. On a hard disk system, a much better approach is to have a 'key' which can be installed on the hard disk, but Xor does not seem to allow this. In general, multitasking and copy-protection seem to be rather incompatible entities, because I can only have two floppy disk keys ready when I boot my system.

Despite all this, Xor is a wonderful product. I enjoyed using it, and I believe it is the way forward - integrated MIDI networks are the way of the future.


No contest! The two programs are so different in their application, their design and their environment, that any comparison is almost pointless.

Hollis Research's MIDIman is a desk accessory MIDI Controller, Processor and System Exclusive Editor program. It is designed to work best in a Trackman environment (but can work with other sequencers) as a utility for controlling effects units, processing MIDI data, and making quick tweaks to synthesizers and expanders. MIDIman has a built-in text-based profile language which enables easy customisation of any profile by the user.

Xor is a complete environment for the creation, graphical editing, storage, indexing and retrieval of a large number of sounds or patches from a number of MIDI instruments. It does not act as a MIDI Controller or Processor, and is designed to work best in Dr. T's own Multi Program Environment. A separate profile editor will be available soon, but given the graphical nature of the editing interface, it can be expected to be more difficult to programme than MIDIman's text-based system.


Xor is a program, not a 'desk accessory'. In the face of programs like MIDIman from Hollis Research, which are DAs, this might seem to be a disadvantage at first. However, this is remedied by Dr. T's Multi Program Environment (MPE).

The MPE is a sophisticated system which lets you use any MPE-compatible program in conjunction with up to 10 others. Thus you could use sequencer data from the KCS sequencer, for example, in a voice editor like Xor. The MPE menu entry makes the other program(s) look something like DAs anyway, since you can just 'switch' between programs at will, but it is the easy transfer of information (dynamic data exchange) between the separate programs which gives MPE its power.

Currently there are over 30 different programs which are MPE-compatible, and more are being developed. Dr. T even produce a do-it-yourself MPE toolkit in the form of TBASIC, a programming language which lets you write your own MPE programs. I know of few other ST-based systems which allow the user to access the depths of the system in such a way.

Naturally, Dr. T are actively encouraging other software companies to write MPE-compatible programs. Without some sort of de facto standard, I can see the ST's current popularity waning in the future in favour of a more 'standardised' multitasking computer like the Commodore Amiga perhaps or the Acorn A3000/RISC range of computers.

Also featuring gear in this article

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Yamaha RTC1

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Digital Signal Processing

Sound On Sound - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.


Sound On Sound - Nov 1989

Donated & scanned by: Mike Gorman


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Software: Editor/Librarian > Dr. T > X-OR

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Atari ST Platform

Review by Martin Russ

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