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Prism 16-Track PC Sequencer

David Mellor unplugs his Atari and tries his hand at sequencing on a PC, using Magnetic Music's 16-track Prism sequencer.

When I bought my PC, early in 1987, there wasn't much choice in the IBM compatible market. Basically you had two options: very expensive - or Amstrad. Being a keen spotter of value for money, I plumped for the Amstrad, despite the connotations it had at the time with cheap and cheerful hi-fi, or should I say lo-fi, systems. Well, to give Amstrad their due, my basic PCI 512 SD with a monochrome monitor has served me excellently as a computer for word processing, spreadsheets, database, and the other standard tools you need to help you through the business day, but one thing I have never considered it for is music sequencing. I have naturally been aware that there are PC-based music programs around, but the choice of computer for music is just so obviously Atari (here in the UK at least, where there is such a vast price differential between Atari and Apple) that using the Amstrad for that purpose has not seemed a particularly attractive proposition to me.

Let's consider for a moment just why the Atari ST has become the major computer for musical applications. The most obvious point in its favour is the inclusion of MIDI ports - you don't have to buy an extra MIDI adaptor to translate computer-speak into musical instrument language. But this is just a minor factor. The wonderful feature of the ST is its high resolution mono monitor. Below the very highest echelons of personal computing, Atari's SM124 and near equivalent SM125 monitors offer absolutely the clearest and best screen displays around, at an amazingly low price. They are ideal for linking musical events with text and graphics to give the composer arguably the best platform for music software there is.

The main alternatives to the ST are three in number: the Amiga, which as yet doesn't have nearly as good a software base; the amazingly expensive Macintosh (how do they get away with it?); and the IBM PC compatible. For those of you who haven't the time to follow the ins and outs of the personal computer industry, a brief history of the PC is follows:

Way back in the mists of time, early 1980s I think, IBM decided to cash in (as if they weren't making enough cash already) on the growing market for personal computers, ie. computers which were cheap enough to have your own rather than share with a lot of other users in an office. The computer they came up with - the PC - wasn't earth shatteringly successful, but where IBM treads, others tend to follow. So, shortly after the PC came an enormous number of PC 'clones' or 'compatibles' - computers made by other companies which would run in a virtually identical way to the IBM original. The huge IBM PC compatible industry has spawned a vast range of software, hardware, improvements, modifications, and add-ons - not to mention an equally vast range of jargon and confusion: PC, AT, XT, 286, 386, CGA, EGA, VGA, etc, etc. You don't just go out and buy a PC like you would buy an Atari 1040 ST or Apple Macintosh SE. There is a lot of product literature to be examined in detail first, to make sure you get the facilities you want, and that you can run the software you need to use. [Several music dealers specialise in PC music applications, and they are well worth visiting/talking to before you take the plunge - Ed.]

To cut a (potentially very) long story short, here I am running a sequencer called Prism on my basic Amstrad 1512 PC compatible. I would imagine that there must be a lot of PC users out there who would like to have sequencing software but don't want to go to the expense of another computer. Also, because there are some PCs with high resolution displays - something which the original Amstrad 1512 doesn't score many points on - coming onto the market at rather attractive prices, it's possible that a PC might be first choice, as long as the software is right.


One nice thing about Atari and Mac software is that you know when you buy it that it will run on your machine. That's because you can ask the dealer the simple question 'Will it run on my XYZ?', and if it doesn't you can take it back and demand a full refund. With a PC, things are different. There are so many possible hardware configurations that the best response you can ever expect from a dealer is a vague 'probably'. I'll mention the problems I encountered, doubtless due to my particular computer, as I come to them.

Prism, as I received it, came on a 5¼" 360K floppy disk, with a manual and a plug-in MIDI interface. The interface supplied is a PC MIDI Card made by a company called Music Quest (those in the industry with long memories may be assured that this is not the same 'Music Quest' name that I once traded under, and have since ceased to use) and comes with an installation disk. The interface plugs into one of the PC's expansion slots, and has a 9-pin connector to which you attach the supplied flying lead with a 9-pin plug and two DIN sockets for MIDI In and Out connections. I didn't find the installation disk at all helpful, once I had located the interface. The software didn't seem to recognise that an interface had been installed and refused to cooperate. I thought I was going to be stuck, but carried on anyway, and in fact the interface did run successfully without the aid of the installation disk.

Prism itself also has to be installed, and there is a utility program on the disk to help you do so. Installation is very easy, either onto a hard disk or floppy disk, and the software can be run from just a single floppy disk drive if required. There are some options to be puzzled over, such as 'interrupt number', but a little trial and error and intelligent guess work will get things working. There is also a choice of display types in the setup routine, including CGA, EGA, VGA (working as EGA), Hercules monochrome, and Yamaha C1. If these initials don't mean anything to you (and I see no reason why musicians should have to involve themselves in such over-complicated computer jargon) then either take a look in your computer's manual to see if you can find a matching letter combination, or make sure that you see Prism running on a system like yours before you buy. CGA mode works on my Amstrad 1512, giving a coarse but usable screen display. For serious work, I would advise investing in a better, higher resolution, screen.


I consider the 'look' of a computer sequencer on the screen to be very important. After all, it's an environment you are going to be spending many hours working in and is the computer equivalent of pleasant wallpaper and soft carpets. At first sight, on my system, I was thinking that I had come down a few levels of sophistication from the Atari and Mac programs I have used and seen. But that was just my basic hardware screening Prism's essential virtues from my eyes.

Prism is a WIMP program (WIMP meaning 'Windows, Icons, Mouse, and Pull-down menus') and offers a very modern, versatile interface to the user. Its mouse-driven operation is more Mac-like than Atari-like, with menus not opening until you click the mouse button and instructions being carried out upon the button's release. Also Mac-like is the operation of the scroll bars - they work properly! Atari owners who have not had the benefit of proper scroll bar operation (some will have, depending on the software in use) will be surprised at how much nicer life with a mouse can be.

The basic Prism screen consists of a number of icons, each of which can be opened up into a window for a particular type of operation. Probably the most-used of these will be the Transport and Track Sheet windows. Others include Librarian, Event List Editor, and a section Link List and Editor. Prism is a pattern-based sequencer, so the first task in recording is to set the default length for patterns, which will automatically be used for all the patterns you record unless you instruct otherwise. To record into a pattern, you pass over to the Track Sheet window where a vertical list of tracks, with scroll bar, is presented along with a horizontal activity display (Figure 1).

Figure 1. Prism Track Sheet (on monochrome monitor).

When it comes to organising MIDI channels, sequencers generally fall into two types: those which record the channel into the track as part of the MIDI data stream, and those which record the data without channel information, but channelise it on the way out. Prism is of the first type, with channelisation of outgoing data from each track available as an option. Being able to record more than one MIDI channel on each track is a necessity with Prism, as it only has 16 tracks. This is a surprisingly small number, compared to other sequencers which offer maybe 60 or 100 tracks [and cost more - Ed.], but since it is possible to mix channels on a track and unmix them later if you wish, it doesn't limit what you can do, it just slows you down a bit.

Actual recording is simple, and the Transport window allows maximum ease of operation with a minimum of mouse clicks. It is possible to record either in 'one shot' mode, where you begin at the beginning of the pattern and record through to the end, or in 'looping' mode, where the pattern will cycle round and round while you add more data. This is not drum machine style recording, however. Loop mode records a series of takes, one for each cycle of the loop. You can then select which take you want to hear from a numbered list in the Record Buffer. If you have recorded a lot of takes in this way, the options can take a bit of time to sort through.

Prism's quantisation features are versatile, offering quantisation during recording, quantisation after recording, and a third valuable option of unquantising something you have recorded with quantisation and have had second thoughts about. As well as the standard (8th note, 16th note, etc) types of quantisation, there is also 'swing' quantisation to help you create those snappy, danceable rhythms. There are further quantisation possibilities available in the Edit Window, which I shall come onto in a moment.


There are two distinct editing environments in Prism, as the clear but wordy manual states. Depending on how precisely you want to home in on the MIDI data, you can either edit by chunks in the Track Sheet itself, or get down to the fine detail in the Event List. The Track Sheet window displays 16 beats of music horizontally, which you can scroll quite easily to look at other parts of the composition. Stars, squares, and dots tell you what happens on each beat of each track. A star or a square means 'something happens', a dot means 'nothing on this beat'. I very much liked the way you can click the mouse on any star or square and hear what happens on that beat. The mouse also selects regions of the track display for editing. By clicking or shift-clicking the mouse on any of the track names, you can select tracks for editing. By doing the same on areas of the activity display, perhaps using the scroll bar to move around the piece, a section of music a certain number of tracks wide and a certain number of beats long is selected. Although editing by the beat is useful for a lot of operations, the section length can be adjusted quite easily by clock pulses.

Once a region is selected, it can be Cut out or Copied and Pasted into other places in the music. You can also Fill a selected region by having Prism repeat a section over and over - this is especially good for creating drum parts. This type of editing is simple and to the point, and you don't have to spend ages figuring things out.

Figure 2. Prism Event List display.

Editing in the Event List, I have to tell you, is a lot of fun! This is probably Prism's strongest point, because you'll end up fiddling endlessly - and probably most fruitfully - with the powerful numeric and graphic tools. Figure 2 shows the basic Event List, which doesn't look very promising at first sight but improves greatly with acquaintance. Unlike some event lists, it is possible here to select just one event, a number of events, or all events for any type of editing operation - such as changing note velocity, duration, etc.

Figure 3. Selection Filter.

An ingenious device called the Post Operator can work wonders in transforming rough and ready MIDI data into the musical and expressive sounds you would like to hear. And by the way, you can do all this editing while the music continues to play and hear the difference it makes almost instantly. Post Operators let you change a number of selected values by adding, subtracting, multiplying, dividing, or randomising them. For instance, you can add 20 to all the velocities, multiply durations by 1.5, randomise the timing of the event by up to a specified amount. Integral to the use of Post Operators is a Selection Filter (Figure 3), which determines which events will be edited. For example, you might want to add 10 to all the velocities of notes below C3 in bars 2 and 3. The Selection Filter works with MIDI Controllers, Program Changes, and other types of data too.

The numeric editing tools are good, but it's when you start using the Graphs that you realise what Prism can really do for you. Here's a list of some of the things the Graphs can do:

Add swing
Vary rhythms
Add accents
Create crescendi
Time reverse
Add variable time shift

Figure 4. Prism's graphic editing window.

There are a lot of possibilities here, and just in case you get too experimental, the Undo function is able to come to your rescue. A typical Graph is shown in Figure 4. There are three different types:

The Mapper is used to change one set of numbers (velocities or durations, for instance) into another set of numbers. For example, if you had a track with velocities ranging from 20 to 110, you could map them to a range from 45 to 75. Everything in between the extremes of the range gets changed to an appropriate in-between value. This is, of course, a very simple example - you could equally turn the data completely inside out if you wanted, and also do some pretty strange stuff to time and note values.

The Time Scaler is simpler, but still powerful, and is used to draw out a graph of values which change with time, such as velocity values increasing during a crescendo. And don't forget that it can work with controllers, time shifts, and pitch transpositions too.

The Time Cycle works in a similar way to the Time Scaler, but whatever you do repeats over and over. Typical uses would include accenting certain beats of a drum pattern, or creating complex types of quantisation far beyond what standard quantisation and swing can do.

The Prism manual provides a good range of examples of all of the graphic editing functions and, before I leave the subject, let me say once again that all of this editing takes place while the music plays on. You are only ever a mouse click away from hearing your music performed according to the changes being made.


I was pleasantly surprised by Prism, even running on a steam-driven computer like my old Amstrad 1512. Perhaps I'm a bit used to seeing PC software which is difficult to use, old fashioned, and generally not nearly as exciting as the things that are available for the ST and Macintosh, but Prism is a very pleasant and modern sequencer to use, despite the small number of tracks, and has vast possibilities in its graphic editing capability. If you own a PC and have been toying with the idea of buying another computer specifically for music, then I would seriously advise a thorough investigation of Prism.

Thanks to Hugh Symons Music Division ((Contact Details)) for supplying the review product.


Prism and PC MIDI card £169 inc VAT.

Distributed by: Digital Music, (Contact Details).

Also featuring gear in this article

Previous Article in this issue

Behringer Studio Processors

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Leader Of The Pack?

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 - Jul 1990

Gear in this article:

Software: Sequencer/DAW > Magnetic Music > Prism

Gear Tags:

PC Platform

Review by David Mellor

Previous article in this issue:

> Behringer Studio Processors

Next article in this issue:

> Leader Of The Pack?

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