8 and 12 Track MIDI SequencersApplications Creation Musical
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The PCW started life as word processor; then other business software started to appear -accounts, databases and spreadsheets; software houses began to see is entertainment potential and brought out a variety of games for the trusty machine. Now, taking the PCW one stage further, DHCP's new MIDI software has brought the power of musical composition to the green screen.

If you already own a synthesizer, or other keyboard of the musical variety, you will Know that they usually have the capability to connect up to other similar instruments for remote control. Computers which have a so-caJled MIDI' interlace can also talk to these instruments.

MIDI stands for Musical Instrument Digital Interface and is the standard way that most modern electronic musical instruments communicate with each other. It was originally used to connect two or more keyboard instruments together to produce more complex sound 'textures'; however manufacturers were not slow to realise that there were many other applications that MIDI could be put to.

The first non-keyboard MIDI devices were sequencers, essentially dedicated computers for storing and replaying MIDI note values. The sequencer records the note values sent to it via the MIDI, together with information controlling pitch bend, velocity sensitivity (how hard you hit the key for touch sensitive keyboards) and voice change. The information is recorded and can be sent back on any one of 16 separate MIDI channels, allowing you to control up to 16 synthesizers or other devices.

Over the past few years there has been an enormous increase in the variety of devices to control or be controlled by MIDI including effects units, mixers, and innumerable rack mounted (keyboardless) synthesizer and sampler expanders. You can play these from keyboards, drum pads, guitars, and various wind instrument (ie. saxophone or trumpet) units.
This means that with the use of sampling technology, a drummer can play bass, a sax player keyboards, a guitarist drums, a bass player percussion, and a keyboard player guitar, all without changing from their normal instrument. It also means that it is possible for solo artists to perform live and reproduce album tracks without backing tapes, extra musicians, or having to grow several extra arms.

What is a synthesizer anyway?

In essence a synthesizer is a device for creating sound electronically that allows you to shape pitch, tone and amplitude. There are two basic types of synthesizer. Analogue and Digital.

Analogue synthesizers work under voltage control, using an oscillator as the basic sound source. Digital synthesizers use digitally stored waveforms which are combined and manipulated within the digital domain to produce sound.

Analogue synthesizers produce the classic synthesizer effects heard on 1970s/early 80s albums by Jean-Michel Jarre. Tangerine Dream and so on.

Digital synthesizers are capable of producing much cleaner and more realistic representations of acoustic instruments, as well as some weird sounds of their own (if you're not careful!) Samplers are synthesizers which are able to digitally record and play back sounds. Samplers are mostly used to record specific instruments that are difficult to synthesize, such as the human voice. However with many current samplers it is possible to sample whole sections of a piece of music and use them in your own composition. Some people, such as the JAMs (Justified Ancients of Mu Mu!) have created entire pieces of music from samples of other people's records.

The copyright and moral problems caused by this sort of use are currently a very controversial area. Some artists, such as Frank Zappa are going as far as copyrighting individual sounds!

Most Hip-Hop and Rap records use extensive sampling, and nearly every Top 50 record seems to have a sampler on it somewhere. Some 12 inch remixes are entirely created by sampling.

Recently the micro-computer has become increasingly popular for MIDI sequencing. Unlike dedicated hardware sequencers, it is easier to edit and manipulate the sequencer data. It is unusual to go into any studio today that does not have at least a basic Micro sequencing package available.

Originally most Micro MIDI sequencers systems were designed for Apple II and Commodore 64 computers, but with the advent of inexpensive '16 bit' computers such as the Atari ST and Apple Mac it is more common to see them in action; there are some extremely powerful packages available for them.

On more expensive sequencer packages, and on dedicated hardware sequencers there are features like Quantisation' which will attempt to assign what you have played to a specified note value, sometimes with very curious results.

You can also record in Step Time' which involves choosing a note length, and playing the notes in any speed you like. However sloppily you play in. the notes come out in the exact time you specified. If you are not careful with this method everything comes out sounding very robotic.

On more sophisticated computer sequencing systems it is possible to show the events on screen and edit from the computer keyboard, allowing very precise control.

8 and 12 Track MIDI Sequencers

So what does the DHCP sequencer on your humble PCW offer? Can it rival the multi-million pound studio setups?

It is essentially an entry level package. You will need to buy the interface unit which is the basic hardware required, and then pick one of the two software options depending on whether the instrument you are connecting to can handle more than 8 tracks or not. At £139.95 for the 12 track (including interface), it is well below the £250-or-more 16 track packages for the Atari (which already has the MIDI interface hardware built in), and cannot be expected to offer the same performance features.

The interface plugs into the expansion port of the PCW. The current model is a sturdy metal box, that can easily be persuaded to fall off under its own weight. This can be got round with a couple of sticky fixers, not an entirely satisfactory solution, but DHCP tell us that they are designing a smaller and lighter interface. Make sure it is secure, as constantly changing leads could well cause problems.

As to the sequencing software, the screen is simply laid out. On the left is a box listing all the tracks and their current status, either Off, Rec(ord), Play, or Loop. There are columns giving the MIDI channel number, the looping status, and the percentage of memory used in each channel. Below this there is a small box with the metronome status - Off. Int(ernal) or Ext(ernal) - the tempo, from 40-250 beats per minute (bpm), the time signature - variable from 2/4 to 9/4 -and the barcount.

At the top right of the screen is the 'modes' menu. Briefly, you can load or save tracks to disc either a single track, or a complete set of 8 (or 12) tracks. You can clear data, either from one track, the whole memory, or the notepad. The notepad area is a space where you can put comments about the current sequence.

Keys 4 and 7 are used to increase values, and 5 and 8 to decrease. You can view a disc directory, which displays the names and types of files (single or multi track).

Underneath the Notepad area are two small boxes, one telling you which track is currently being recorded and the other is a bargraph which gives you an indication of what percentage of memory you've used on the current track.

Is this a record?

Before recording your first track you decide whether you want to hear the metronome or use an external device, such as a Drum machine. If you are using the metronome you then enter your time signature (default is 4/4), and the tempo. Having completed these highly technical operations you then go into record mode by placing the cursor over the relevant track mode sector.

Here you have the choice of recording/playing or playing only. When recording the barcount tells you what bar you are on. and the bargraph tells you how much memory you have used.

The sequencer not only records the note information, but also keyboard velocity (how hard you hit the key-board) so if you are using a touch sensitive keyboard like a Yamaha DX7 or Ensoniq ESQ1. it will play back with your sensitive interpretation intact. It also records any voice changes you make while playing. For some reason neither of these features are noted in the documentation.

If you use over 98% of the track memory, a message comes up to tell you that the buffer is full, and stops recording, though you have to stop the sequencer manually.

Before playing this back you can set the MIDI channel. This can be altered at any time after you have recorded, a very useful feature which allows you to change which instrument is being played, something that many dedicated hardware sequencers won't do.

You can also change the tempo and the time signature. It is possible to change from 4/4 to 9/4 for example, which gives interesting, though not necessarily musical, results.

Listen with MIDI

All the tracks are recorded in the same way. You can hear the tracks you have previously recorded as you lay down a new track (this is hip musicians' jargon for recording; don't forget to wear shades and chain-smoke Gauloises as you lay tracks down), or turn them off until you've finished. The Loop facility allows you to play back just one section of a track, so if you want to just repeat bars 5-10 it will do this for you.

It also allows you to start playback of the track at any point. This facility is programmable separately for each track, which can give you hours of fun. By recording a number of tracks and looping portions of them, it is possible to build up quite complex shifting patterns from very simple sequences. Very Brian Eno!

Unfortunately it is not possible to edit the tracks once they've been recorded, (except looping), so if you make a mistake, you have to record the track again.

All information is recorded in 'real time' that is it plays it back to you exactly as you played it, so it helps to have practised your piece before recording. DHCP are developing an editing program to work with the sequencer, but they were not able to give us any further details at present time.

MIDI Modes

MIDI has lour separate modes ol operation lhal It uses to address Instruments they are:

  • Mode 1: Omni on, Poly. Voice messages are recognised on all channels and play all voices polyphonlcally (ie. more than one note at a time)
    Mode 2: Omni on, Mono. Voice messages ate recognised on all channels, but only monophonlcally (ie. one note at a time)
  • Mode 3: Omni off, Poly. Voices are transmitted polyphonlcally only to Instruments on a specillcally assigned MIDI channel (1-16)
  • Mode 4: Omni off , Mono, This mode is used for specific voice assignments to a multi-timbrel synthesizer (ie, a synthesizer capable of producing several dlllerent voices at a time),

Each voice is assigned its own MIDI channel. Instruments capablo ol supporting this mode are the mosl useful for Inexpensive multi-channel sequencing. Synthosizers with Mode 4 will normally support Modes 1 and 3 as well,

On an Increasing number ol current synthesizers there is a new version called Omni off, Multi, which performs In the same way, but polyphonlcally.

When you are finally happy with your opus, you can then store it on disc. You give the piece a name, and the PCW saves not only the music, including looping information and MIDI channels, but any information on the notepad. It is possible when loading or saving to pick all the tracks, or just one. This is an interesting idea and enables you to combine tracks from several different sequences. Very Stockhausen!


The DHCP sequencer package, though inexpensive, has some interesting features and is able to provide a good introduction to using computers in music even though the PCW was not really intended for this kind of thing. The documentation is brief and to the point, and the program is well designed and user-friendly', so you should have no problem running it.


★ YEAR: 1987
★ PRICE: £45(8 Track); £60(12 Track); Interface £79.95


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L'Amstrad CPC est une machine 8 bits à base d'un Z80 à 4MHz. Le premier de la gamme fut le CPC 464 en 1984, équipé d'un lecteur de cassettes intégré il se plaçait en concurrent  du Commodore C64 beaucoup plus compliqué à utiliser et plus cher. Ce fut un réel succès et sorti cette même années le CPC 664 équipé d'un lecteur de disquettes trois pouces intégré. Sa vie fut de courte durée puisqu'en 1985 il fut remplacé par le CPC 6128 qui était plus compact, plus soigné et surtout qui avait 128Ko de RAM au lieu de 64Ko.