The first surprise for me is that it wasn't invented in Japan, which I just assumed because all the best-known FM chips and synthesizers are from Japan.
Early electronics from Japan were often seen as inferior products compared to the American and European products (RCA, Westinghouse, Philips, Telefunken, etc). Japan of yesteryear was the China of the 1990s and early 2000s, some decent stuff but a lot of cheap clones. Now, China makes everything so that analogy falls apart today. The 1970s oil crisis was one of the major events that helped bring Japanese goods into a better light, Japanese cars were absolutely killing the domestic automakers on fuel efficiency and price and rather than engage protectionist tariffs (Chinese EVs today, hmm?), they forced the domestic automakers to try harder. This change in public perception helped give a real sales boost to other manufacturing sectors, like consumer electronics which in turn helped drive innovation in a very short time period. That's not to say Japanese product was junk in the 50s and 60s, there were a few dominant players of quality products (Sony) but like Chinese manufacturing today, there was still a lot of cheap junk.
Did he? Wasn't there New England Digital (NED) with the Synclavier which had FM on the market before Yamaha? Are you sure Chowning gave licenses? I would rather expect that this was the Standford administration's business, not Chowning's.
Then came Yamaha, who saw its potential, and made a fortune with it. So did Stanford. That patent became the second most successful patent Stanford ever had until it expired in 1996 (by now obv the university has had way more financially successful patents).
It secured Chowning his tenure; the university probably wouldn’t have prolonged it otherwise. Quite an incredible story the whole thing.
Even more with Chowning's background as a musician, not an engineer.
> Multiplying sounds just sounded too ridiculous
Is this really the "official" reason, or your interpretation?
Stanford did reach out to the American synth manufacturers looking for a company to license the patent. If I recall correctly, the problem wasn't that they didn't get it, the problem was that they weren't interested in, or capable of, building digital synths^1. At that time manufacturing LSI chips for synthesisers was absolutely cutting edge, and Yamaha had taken a major gamble in developing their in-house semiconductor manufacturing capability. Because of that, Yamaha were pretty much the only synth company capable of doing it.
1: The prototypes for the first-generation Yamaha FM synths were built with discrete components, and were enormous. It's understandable that it wouldn't be economical unless you could manufacture your own LSI chips.
Didn't the Synclavier have FM and was on the market even before Yamaha? So I would assume that at least NED must have been interested and have the capabilities of implementing FM.
Check out how complex the design of the Synclavier is: http://www.studiorepair.com/gallery/misc/NED_Synclavier_II/ (and this is the more modern Synclavier II!) It's huge, and cost a fortune. I'd totally understand a company not wanting to manufacture and market it.
AM (amplitude modulation) is multiplication. When you do it fast, you get what's commonly called a ring modulator.
Can't vouch for this but from what I've read the 2025 remake (Highest 2 Lowest) is...not good.
E.g. Akai working with Roger Linn on MPC and Chris Huggett on the S1000 sampler.
Or Dave Smith working with Yamaha and Korg on physical modelling and wave sequencing.