General Description - Sequential Max Operation Manual

GENERAL DESCRIPTION
A compact, affordable musical tool, the MAX contains functions until now provided
only by a synthesizer in combination with a multi-track tape recorder. The block
diagram (next page) shows the main sub-sections: keyboard, recorder, sound memory,
voices, and MIDI. Using this as a basis for discussion, we trace backwards from the
audio output, to see how the sub-sections work together.
The audio output comes from the six independent synthesizer voices. In contrast to
homophonic synthesizers, which program each voice with the same sound, each of the
MAX's voices can have a different sound. Each voice has a multi-waveform oscillator
(or noise) as the principal sound source. The oscillator drives a resonant low-pass filter
which contours the timbre, and an amplifier which contours the dynamics. There are
three attack-decay-su stain-release (ADSR) envelope generators: for oscillator
frequency, filter cutoff frequency, and amplifier gain. (The polarity of the first two can
be inverted.) A triangle- or square-wave low frequency oscillator (LFO) can modulate
oscillator frequency, pulse width, or filter frequency. A second modulation route runs
from the oscillator triangle output to the filter frequency, for frequency modulation
(FM). Frequency glide ("portamento") and voice volume are programmable.
A voice has two types of inputs. First are the sound parameters from the sound
memory. These operate on the synthesizer voices to define the track's timbre—in other
words, the instrumental sound. The parameter memory contains 80 permanent sounds (in
ROM). You can't change these sounds. But the RAM area of memory accepts up to 20
sounds which can be loaded from an external MIDI device. For example, you can use the
SCI Model 610 Six-Trak to develop custom sound programs, then send them to the MAX
over MIDI. (For more information on programming sounds, please see the MAX
MIDIGUIDE.) The MAX sounds can be selected either with the keypad or by a MIDI
sound selection command.
The second type of input to a voice are the notes. Notes tell the voice when to play and
what pitch to play. A voice can be played by notes coming from three sources: the
keyboard, the recorder, and MIDI.
When playing the MAX keyboard "live," the six voices are each programmed with the
same sound (homophonic mode). Live multi-timbres are not possible because the MAX
cannot know which keystrokes you intend for which timbres.
But the recorder can record whatever you play on the keyboard as a separate track
using its own voice. So each track can be overdubbed with a different sound. The
recorder allows overdubbing and editing without re-recording, splicing, or accumulating
noise and distortion by "mixing-down" and "bouncing" audio tape tracks.
Lastly, the voices can also play notes coming in from MIDI, which may be from another
synthesizer or external sequencer.
Both the sound RAM and the song memory are volatile—they lose memory when you
switch power off. To save songs permanently, you can "dump" them to the external
MIDI recorder. The MAX can send live notes, recorded notes, or sounds out to MIDI. For
example, SCI's Model 64 Sequencer for the Commodore 64 and associated software
offers increased recorder storage (up to 4000 notes), sound program storage on cassette
or disc, song transposition, and alternate keyboard modes, as well as forthcoming music
display and editing functions. Finally, if you use a MIDI rhythm unit (such as the SCI
Model 400 Drumtraks), it sends a MIDI clock to the MAX recorder, which synchronizes
the MAX song to the drum song (or pattern).
For more information on the synthesizer voice parameters and MIDI applications, please
see the MAX MIDIGUIDE.
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