Creating Sounds - Yamaha PSS-680 PortaSound Authorized Product Manual

As you can see, the different ratios produce totally different
wave forms — saw-tooth waves give a bright tone color sui-
table for strings and brass, while square waves sound milder
and "simpler", having fewer harmonics (overtones), and are
good for woodwinds like clarinet and oboe.
To generate the basic sine waves, the PSS-680 uses digital
oscillators called "operators" in FM synthesis. The basic
configuration of theses operators is shown on the front panel
illustration reproduced here.
The two "boxes" (with the triangles in them) represent the
two oscillators, marked in blue as
OPERATOR 2. The output from OPERATOR 1 is fed to
the input of OPERATOR 2, thus modulating the second
oscillator. As you have just seen, this causes it to oscillate
in a different way, producing a different sound than the simple
sine wave tone.
You can try out the effect of such modulation right away.
At the moment, with the SINE WAVE voice, OPERATOR
1 is NOT modulating OPERATOR 2 at all — that is why
you hear nothing by a sine wave in the first place. Check this
by pressing the MOD. LEVEL button in the DIGITAL
SYNTHESIZER section. The TEMPO/PARAMETER &
VALUE display will change to
As you can see, the MODULATION LEVEL parameter
, which determines how strongly operator 1 modulates
operator 2, is set to 00. This means there is no modulation
in this voice — but you can change that. Raise MOD. LEVEL
by holding down the + VALUE button while playing the
keyboard. Notice how the sound becomes brighter and
sharper, particularly over a value of 50.
Finally, set MOD. LEVEL to 80. Compare this sound to the
original SINE WAVE voice by pressing – and + at the same
time to revert to the original modulation level value of 00.
Unless you store them in the memory banks BANK 1 –
5 (12a), your original sounds will be lost as soon as you
switch to a different voice.
OPERATOR 1 and
Set MOD. LEVEL back to 80, then save this new voice to
memory BANK 1. This makes it easier to compare the new
voice with the original SINE WAVE sound.
•
How to save voices to any of the five BANKS was ex-
plained on p.8 ATIP. Simply hold down the red STORE
button (12b) and simultaneously press the desired BANK
selector (12a), for example BANK 1. The VOICE/STYLE
display will indicate
working on is now stored in BANK 1 and can be recalled
any time by pressing that button.
You can select SINE WAVE by entering "99" with the VOICE
SELECT buttons, and the altered voice with BANK 1. When
you switch between them, the TEMPO/PARAMETER &
VALUE display shows their different MOD. LEVEL value.
b) Modulators, Carriers, Envelopes
Before you can use the rest of the parameters to create sounds,
it is necessary to understand a bit more about FM Synthesis
theory. Once you have got to know the concepts of
"modulator", "carrier" and "envelope", you will hear how
they actually determine the characteristics of each voice.
The left row of buttons — ATTACK RATE, DECAY RATE
and FREQUENCY — accesses identical parameters for op-
erators 1 and 2. However, due to their different roles in FM
synthesis, the settings affecting operator 1 have a very dif-
ferent influence on the sound than those for operator 2.
Since OPERATOR 1 modulates OPERATOR 2, it is called
a "modulator". It is responsible for the tonal quality of a
sound. OPERATOR 2 is referred to as a "carrier" because
it "carries" the sound, determining its volume.
Within the two OPERATOR boxes is a white triangle called
an "envelope" — a representation of the change in operator
output level over time. It consists of two parameters, AT-
TACK RATE and DECAY RATE. "Attack" is the time it
takes for the level to rise from 0 to peak value, while "decay"
is the opposite — how long it takes for the level to drop from
its peak back to zero.
You can now listen to how all of this relates to actual sound
synthesis while continuing to alter the sound you have stored
in BANK 1.

3) Creating Sounds

ATTACK RATES
To see how the attack works, call up parameter
ATTACK RATE for OPERATOR 2, the carrier. The
TEMPO/PARAMETER & VALUE display should show
The voice you are currently
i.e. the
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