Yamaha EMQ-1 Manual download pdf (Page 30)

PART

III

ADVANCED FUNCTIONS

DIGITAL SYNTHESIZER

Like a Yamaha DX synthesizer, the PortaSound PSS-680 uses an FM sound source — and like a digital

synthesizer, it lets you, adjust various voice settings (parameters) in order to create your own original

sounds. Five of these

custom voices can be stored in special memory banks.

The following short basic course on "FM Synthesis" which will help you understand this process, making

it easier for you to achieve the kind of sound you have in mind.

While this paragraph explains in detail how the voice parameters work together, their functions are

summed up in the next section, SYNTHESIZER PARAMETERS, for easy reference. You may want to read

that section first for a quick overview.

FM SYNTHESIS BASIC COURSE

Voice Parameters and Values

A Bit of FM Theory

The preset voices are edited (altered) by changing the values

of nine voice parameters (selectors 12c). These settings de-

termine what a voice sounds like by each adjusting a different

aspect of the tone. The controls for the DIGITAL SYN-

THESIZER section (12) are located under an illustration

(12d) that shows how these parameters are interrelated, giving

their names and numbers. It is reproduced further below for

your convenience. (The small numbers next to the parameter

numbers in the illustration are the respective value ranges

of the parameters.)

How to alter parameter values has already been explained

on p.10 in the PARAMETER CHANGE paragraph. Pressing

the parameter selectors (12c) calls up the value of each pa-

rameter on the TEMPO/PARAMETER & VALUE display

(9). The single digit left of the dot on the display indicates

the PARAMETER number/symbol. The two digit number

to the right of the dot is the current VALUE of that parameter.

The only difference to note here is that the parameter

selectors in the left row access two parameters each. This

is indicated by their having two numbers (e.g.[0/1]) printed

on them, Repeatedly pressing any of these three selectors

switches between the two parameters shown on the selector

you pushed. The parameter number on the display will

alternate accordingly.

Once a parameter is called up on the display, you can change

its value with the –

and + VALUE buttons (10).

The following explains how the parameters influence the

instrument sound. While reading this information, you will

be making various settings so you can actually hear how a

voice is created step by step.

a) Modulation

Select voice 99, the SINE WAVE. Play the keyboard and listen

to the tone. Press a single note, and it sounds like an electronic

signal. Play a chord, and it is more similar to a cheap electric

organ.

As the voice name says, this is the sound of a pure sine wave.

It is the shape of such waves that determines the character

of a sound —

a violin and clarinet sound different because

they produce a different wave shape. A sine wave looks like

this:

All FM sounds are based on such sine waves — one sine wave

is used to modulate, or interact with, a second one, thus

changing the sound quality. In fact, FM is short for “Fre-

quency Modulation”,which is the sine wave interaction

method your PortaSound uses to produce all the realistic

sounds you have already tried out.

Depending on the frequency ratio of the FM sine waves, the

resulting wave form will differ. The following two examples.

show what happens when a sine wave with a frequency of

250 Hz modulates another sine wave of the same frequency

(ratio 1:1), and when it modulates a 750 Hz sine wave (ratio

1:3).

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Yamaha EMQ-1 Manual Page 30

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