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I read somewhere that PSG is based on squarewaves, which is correct, but who said that the FM music was based on sine waves?! Sine waves tones without any "overtones" (or whatever you call it) at all, so it can't sound like different instruments with different filters. If you filter any wave with a some sort of muffle filter enough, it will reduce all overtones and sound like a sine wave.

In my opinion, the FM music sounds like squarewaves, sawwaves, sinewaves, trianglewaves and noises that are mixed into different sounds with different filters and by combining each other, and use different volumescaling- and vibratoeffects to simulate different instruments. Am I wrong?

Quote

> In my opinion, the FM music sounds like squarewaves, sawwaves, sinewaves, trianglewaves and noises that are mixed into different sounds with different filters and by combining each other, and use different volumescaling- and vibratoeffects to simulate different instruments. Am I wrong?

Not entirely.

Here's what I know about FM synthesis:

FM stands for frequency modulation, and modulation basically means 'to change or alter'. Basic FM consists of two components, a CARRIER, which is a sine wave-- but can be any type of waveform-- and a MODULATOR, which is a second waveform that alters the CARRIER.

There are two main methods for FM synthesis. The first method is called ADDITIVE synthesis, in which the values of both the CARRIER and MODULATOR are added together, divided in half, and then a sine wave is created from that value.

The second is called, well, MODULATION synthesis (I think). In this method, a certain percentage of the MODULATOR is added to the value of the CARRIER, and then a sine wave is created based on the new CARRIER value.

In either type of synthesis, the volume envelope for each OPERATOR (that is what the CARRIER and MODULATOR are called) may be altered to change the resulting sound. In modulation synthesis, the amplitude of the MODULATOR affects the flavor of the final sound. High values can change a sine wave into more of a sawtooth wave, and very high values can create white noise.

If the CARRIER and MODULATOR frequencies are multiples of each other (e.g., 440Hz CARRIER and 110Hz MODULATOR), the sound is melodic. If the frequencies are NOT multiples of each other, then the resulting sound is percussional.

Here is the equation for digital modulation FM:

Waveform = Amplitude * sin[(CARRIER * sample_now) + (MODULATOR * time * input_percentage)]

The values of CARRIER and MODULATOR (in radians) are found by the following equation:

CARRIER = (2 * pi) / (SAMPLE_RATE / CARRIER_Hz)
MODULATOR = (2 * pi) / (SAMPLE_RATE / MODULATOR_Hz)

If you want to know what radians are, take a trig class. ;)

That's about all I know.

You might also want to check out the following site:
http://www.geocities.com/SiliconValley/Campus/8645/synth.html

gym2mid home page

Author	Message
Martin Skog Guest	FM music is not based on SINE waves, is it?! Posted: Fri Nov 09, 2001 7:21 pm
Martin Skog Guest	I read somewhere that PSG is based on squarewaves, which is correct, but who said that the FM music was based on sine waves?! Sine waves tones without any "overtones" (or whatever you call it) at all, so it can't sound like different instruments with different filters. If you filter any wave with a some sort of muffle filter enough, it will reduce all overtones and sound like a sine wave. In my opinion, the FM music sounds like squarewaves, sawwaves, sinewaves, trianglewaves and noises that are mixed into different sounds with different filters and by combining each other, and use different volumescaling- and vibratoeffects to simulate different instruments. Am I wrong?

Paul Jensen Joined: 29 Jun 1999 Posts: 254 Location: California, USA; Hiroshima, Japan	Yes, they are. I'm not an expert, but... (more) Posted: Sat Nov 10, 2001 7:18 am
	Quote > In my opinion, the FM music sounds like squarewaves, sawwaves, sinewaves, trianglewaves and noises that are mixed into different sounds with different filters and by combining each other, and use different volumescaling- and vibratoeffects to simulate different instruments. Am I wrong? Not entirely. Here's what I know about FM synthesis: FM stands for frequency modulation, and modulation basically means 'to change or alter'. Basic FM consists of two components, a CARRIER, which is a sine wave-- but can be any type of waveform-- and a MODULATOR, which is a second waveform that alters the CARRIER. There are two main methods for FM synthesis. The first method is called ADDITIVE synthesis, in which the values of both the CARRIER and MODULATOR are added together, divided in half, and then a sine wave is created from that value. The second is called, well, MODULATION synthesis (I think). In this method, a certain percentage of the MODULATOR is added to the value of the CARRIER, and then a sine wave is created based on the new CARRIER value. In either type of synthesis, the volume envelope for each OPERATOR (that is what the CARRIER and MODULATOR are called) may be altered to change the resulting sound. In modulation synthesis, the amplitude of the MODULATOR affects the flavor of the final sound. High values can change a sine wave into more of a sawtooth wave, and very high values can create white noise. If the CARRIER and MODULATOR frequencies are multiples of each other (e.g., 440Hz CARRIER and 110Hz MODULATOR), the sound is melodic. If the frequencies are NOT multiples of each other, then the resulting sound is percussional. Here is the equation for digital modulation FM: Waveform = Amplitude * sin[(CARRIER * sample_now) + (MODULATOR * time * input_percentage)] The values of CARRIER and MODULATOR (in radians) are found by the following equation: CARRIER = (2 * pi) / (SAMPLE_RATE / CARRIER_Hz) MODULATOR = (2 * pi) / (SAMPLE_RATE / MODULATOR_Hz) If you want to know what radians are, take a trig class. ;) That's about all I know. You might also want to check out the following site: http://www.geocities.com/SiliconValley/Campus/8645/synth.html gym2mid home page

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