The Western Master System should had FM from the start, period. It would have truly blown the doors off the NES. The Japanese Master System has the FM chip built-in. The precursor to it, The Sega Mark III, had the FM Sound Unit, that plugs into the card input slot.
@NintegaRadio - Some of the games DID. Only, of course, if they were compatible with the software at hand. The sounds of the original would play alongside that of the added in FM synths, usually anyway. I know one of the games compatible was the first release of OutRun on the Sega Master System (I had the Anniversary Box earlier, that's how I know)
@NintegaRadio - Or, lemme correct myself here, the sound of the FM synth tracks would replace that of the original sound. I was directed to this high-quality video via an upload of the same bios as seen here, without the FM chip enhancing the sound!
![[SMS] マスターシステム -Sega Master System Demo- FM音源](/img/logo.svg){kind=logo}
