Music & Midi

By Ed McGlone, ed@mistered.demon.co.uk

If you fancy writing some music but haven't taken the plunge maybe this
primer by Ed McGlone will make the difference...

Back in 1988 I was working full time as a musician at around the time
recording studios started to use computers for recording and
composition. I decided to buy my own and opted for the Atari ST instead
of an Apple Macintosh because it was much cheaper, had a similar
graphical interface and included the all important MIDI sockets as
standard.
This combination of features combined with a rapidly expanding software
base swept the ST to success around the world and hit records have been
made using STs ever since!

Many of the sounds you hear in modern recordings are not real
instruments at all but electronic imitations created using
synthesizers. The Beatles used this to great effect on the Sergeant
Pepper album. The instruments were recorded on multi-track tape
recorders which could have 4, 8, 16 or even 24 separate tracks compared
to the two tracks available today on most domestic stereo cassette tape
decks.

Usually each part, the drums, bass, guitars, piano, voices etc. are
recorded separately onto individual tracks. This makes for easy editing
and enables one person to play all of the instruments, as pioneered by
Mike Oldfield on the Tubular Bells album.

The Cubase Arrange window. Each rectangle represents a different
musical part. Songs play back from left to right

Because many song parts were already created electronically it was a
logical step to use a computer to control synthesizers directly. Parts
can be played into a computer which records exactly which notes are
played, when they were played and how hard the keys are hit. The
computer feeds this information via the synthesizers, so the musician
can hear it, and the information is also available in computer memory
so it can be saved to disk. This means performances can be recreated by
the computer on demand and crucially, using the correct software, can
be edited. Apart from correcting mistakes edit features can play the
music in different keys and modify the original performance as desired.

The same piece of music shown in the Key Editor (Piano roll effect) and
the Score Editor (Music Notation)

The MIDI standard enables the information for 16 different instruments
to be sent down one cable simultaneously and this had a dramatic impact
on the way music is recorded and written.

Using an ST song arrangements can be edited and perfected by the
producer long after the musicians have gone home. On the other hand
musicians could record, program and edit tracks at home before buying
expensive studio time -everyone benefits.
Today most recording studios still have an ST available for use and
many musicians still prefer them because they're reliable and simple to
use. Cubase and Notator, the two most popular pro music packages, were
originally developed on the ST and despite switching developing to
other platforms the sheer number of Atari copies sold over the last
decade means probably over half the computers used for music are
Ataris.

Getting started


You'll need an Atari machine with 1Mb memory or more. 512K machines can
run some of the smaller music packages but since memory is cheap and
easy to fit there's no point struggling with less.

A MIDI keyboard. Most keyboards include a MIDI interface. If the manual
is long gone look for a pair of five pin DIN sockets and they'll almost
certainly be MIDI in and out sockets.

Two MIDI leads. One runs from the keyboard to the computer and the
other completes the loop from the computer back to the keyboard.
Software. There's plenty to choose from on old magazine cover disk
giveaways and PD/Shareware libraries to get you started. Hold of making
a commercial package until you know your requirements.

The Digital age

The introduction of the Compact Disc in the mid eighties changed the
way we create and listen to music forever. For most listeners the CD
format offers reasonably priced access to snap, crackle and pop free
audio.

How do they do that?
Sound is carried through the air as vibrations and what we "hear" is
the air pushing against our eardrums. Virtually all methods of
recording and replaying sound, from a wax cylinder phonograph to the
conventional tape recorder, maintain a direct relationship between the
original sound (vibrations) and the recorded sound. A simplistic model
of the recording process goes something like this:

Vibrations in the air are picked up by a microphone and converted into
electrical vibrations. These are amplified until they are large enough
to cut grooved patterns into the master disk which is duplicated using
vinyl. During playback vibrations are converted back into electrical
vibrations as the needle is dragged along the grooves and amplified
until they are large enough to drive a loudspeaker. The loudspeaker
pushes and pulls the air causing sound waves and we're back where we
started.

This process is susceptible to degradation, scratches on a record and
the background noise on tape are two obvious examples. It's bad enough
for the end listener but during creation with maybe 48 separate tracks
all playing back simultaneously the reduction of tape hiss has become
an expensive obsession. Digital audio, as the name suggests, changed
this process to handle sound as numbers, our model changes:

Vibrations in the air are picked up by a microphone and "sampled" many
times a second. Each sample is assigned a number indicating the
loudness. By converting the numbers back into vibrations, through a
loudspeaker, the original sound is reproduced.
The sound quality is dependent on the range of numbers available and
the number of samples taken. Sixteen numbers equates to 16 bit
resolution and is the accepted standard for CD reproduction. In much
the same way our eyes are fooled into seeing continuous motion at 24
frames per second our ears hear continuous sound at 44,000 samples per
second (44.1kHz) and this is the standard set for CD quality
reproduction.

CAF in full flight, the topped monitor window shows output level meters
for each of the eight audio tracks used in the song

With digital audio the sound is reproduced from a detailed set of
instructions, not the original recording, and it's this which makes
digital audio so interesting. When copying digital audio, you are
merely copying a sequence of numbers so the copy is identical to the
original with no degradation whatsoever.

Editing audio parts in CAF's Audio Editor

Sounds can be manipulated mathematically. For example, to add two
sounds together, the appropriate calculation is performed and the
resulting sound is created without degradation.

Most early digital audio was recorded onto tape. Because tape is a
"linear" format you have to wind through the full length of the tape to
get from the start to the end of the tape. Using a hard disk to store
the numbers makes it possible to jump to any point in the recording at
will, this is called "non-linear" playback.

Cubase Audio, one of the leading music applications, combines the
features of a MIDI sequencer and a digital, non-linear, audio recorder.
Recordings can be copied, mixed together, processed, cut and pasted
without degradation. It's even possible to perform most of these
operations in real time while the recording is being played back
without affecting the original recording! This is called "non
destructive editing" where, if you don't like the changes you've made,
you can simply throw them away and the original files remain intact.
The resulting audio files can be edited and edited interactively on
screen and the computer becomes the heart of a sophisticated recording
studio.

This flexibility comes at a price, Digital audio eats storage space for
breakfast! CD quality audio (16 bit at 44.1kHz) requires around 5Mb of
storage for each minute of sound. A Falcon030 can process up to 8
tracks simultaneously so a five minute song, using all 8 tracks
continuously, requires around 240Mb of storage. Typically musical parts
do not last the entire duration of song and repeated sections only need
to be stored once so the overall storage requirement can be reduced
considerably. The largest five minute song on my hard disk occupies
153Mb in 18 separate audio files.

Only machines like the Falcon030, AV PowerMacs, Silicon Graphics, Next
and Sun have the necessary hardware built into the box to cope with
this level of audio manipulation but external units are available to
extend this capability to STs. Stand alone hard disk recorders are also
starting to appear and although tape is not yet redundant the
obituaries are being prepared!

Formats


Some of the different digital audio formats available for domestic use:
DAT
Digital Audio Tape, the professional standard for stereo master
recordings, from £500 upwards.
DCC
Digital Compact Cassette - Phillips "new" format. Uses file compression
and so the reproduction is not quite up to the standard of DAT - but
most people will not be able to tell the difference, from about £160.
CD
Typically read only, so you can't record, but a new generation of
affordable rewritable CDs are just hitting the market.
Minidisk
New Sony format which looks like a small CD. Minidisks can record up to
70 minutes or so and uses file compression, like DCC, (above) from
around œ400.
Nicam Stereo
Nicam video recorders record digital stereo audio tracks. The sound is
16 bit but I'm not sure what the sampling rate is! Early machines were
around 24kHz but even so provided excellent sound quality, from about
œ300.
Incidentally, the first widely available digital audio recording system
was an add-on box for the Sony F1 video recorder. This was an
exorbitantly priced and highly desirable bit of early eighties
technology destined to become a museum piece, you mark my words!

Questions and Answers



What computer do I need for MIDI music?
Any ST will do. Most modern music software requires at least 1Mb of
memory so if you still have a 512K machine, now is a good time to buy a
memory upgrade.
Most commercial software such as Cubase and Logic run best in ST high
resolution (640x400) so get hold of a high resolution mono monitor if
possible. For casual or emergency use a TV running in medium resolution
or ST high, via a mono emulator, will get the job done.

What does my keyboard need to have?
As a bare minimum, MIDI in and MIDI out sockets. The MIDI out on the
keyboard is connected to the MIDI in socket on the side of the ST and
this feeds MIDI signals into the computer. The MIDI in socket on the
keyboard is connected to the MIDI out on the computer and this feeds
MIDI signals from the computer to the keyboard.

Where does the sound come from?
From your keyboard. Think of the ST as a tape recorder which instead of
recording sounds, records exactly how you play the keyboard - in other
words, it records your performance. On playback, the computer is
telling the keyboard to play notes exactly as if you are playing them.

Can I record more than one part?
Almost certainly. A better question would be "Can I play back more than
one part?" This is entirely dependent on the capabilities of your
keyboard. Look for something which says multiplay, multitimbral or
similar phrase. You should be able to choose a MIDI channel or part
number and define which sound should be used by that channel. For
example piano might be channel 1, bass channel 2, and so on.
Not all keyboards have a multiplay section so if yours hasn't, you'll
have to settle for a single sound at a time.
What do I need to use digital audio?
You'll need a Falcon030. The ST can be upgraded with external audio
hardware but this tends to be more expensive than a Falcon030 which can
do the job straight out of the box (although for quality work ensure
the machine has the latest sound modifications fitted). There's plenty
of software to get you started ranging from Atari's Winrec up to
commercial software costing hundreds of pounds. There are even a couple
of sequencers which allow audio samples to be mixed with MIDI music but
you're going to need at least a 4Mb Falcon030 to achieve anything
worthwhile.

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