While RAM often ends up scarce on an ESP8266 with around 40 kB or so ... But it does share a lot of the ESP32 standouts: the LEDC (PWM) peripheral and the unique parallel I2S come to mind.

Of course, you could get rid of the nice-sounding DAC chip and output 5-bit PWM directly from the ESP8266, but aside from being a nice quick demo, it’s going to sound like crap. The other ...