Exploring Yamaha's FM Synthesis Chips

Yamaha's FM Synthesis chips were ubiquitous for many years, in synths, keyboards, and PC soundcards so it's fair to say have been pretty influential to the sonic landscape we've become familiar with. This incredible series from Things Made Simple takes a look at the chips, with a proverbial deep dive on the YM3812, in ten stages... 

YM3812 Part 1 – Register Basics
YM3812 Part 2 – FACE Reveal
YM3812 Part 3 – Behind the Code
YM3812 Part 4 – MIDI Journey
YM3812 Part 5 – MIDI Polyphony
YM3812 Part 6 – Patches
YM3812 Part 7 – Percussive Maintenance
YM3812 Part 8 – Velocity Sensitivity
YM3812 Part 9 – Synth Card
YM3812 Part 10 – Pitch Bend

Here's an excerpt from Part One: 

Introduction

In conducting a pretty extensive deep dive into Yamaha's FM synthesis chips, I've come to realize that while these chips produce very unique sounds, they are also largely very similar. In fact, if you compare their register settings (and ignore the level of granular control that you get), you can see just how many of the settings are the same:

Comparison of Yamaha FM Synthesis Chips

With all of these similarities in mind, I originally planned to build a single module with a variety of sound processor types all controlled by a single microcontroller. After breadboarding this idea out with a YM3812, YM2151 and even a non-Yamaha SN76494, it worked! And I was even able to translate chip settings from one chip to another seamlessly. But when I started to document how it worked, I realized from a complexity standpoint, I needed to back waaaay up and start from the beginning. To get into the advanced stuff, we need to start with a smaller project that lays a strong foundation. And what better foundation than a Eurorack module powered by Yamaha's YM3812 OPL2 sound chip. A chip that revolutionized computer audio for the video games of my childhood.

This article is only the first in a series. Together, we will tour the properties of the YM3812, design the hardware for a module and write the supporting microcontroller code. Hopefully, each article will pair with a YouTube video on the subject as well.

Read part one here: https://www.thingsmadesimple.com/2022/11/28/ym3812-part-1-register-basics/

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