Background: I recently made a project which emits pure tones on a speaker, and it got me thinking about how I was restricted to simple pitches. How would I simulate a chord if I can only play one frequency at a time?
The approach that makes the most sense to me would be to take multiple PWM outputs, each at a component frequency, and feed them into a summing amplifier. Perhaps they'd also need to be level shifted first (assuming for example 0V to 5V square waves in the PWM to -2.5V to 2.5V) to avoid it becoming a purely additive process. Either way I believe I understand the concept there.
But consider a scenario where I'm using a system where other PWMs are already allocated and I need to use just 1. This question's answer addresses it but I don't really follow it. I'm not sure where I get lost but to me I feel like this would just result in some other pure tone somewhere between the two. It's not clear to me exactly what the user is calculating when "adding those phases to two phase accumulators, look up their values in the sine table, add them, and set a PWM output to that value." What does adding them actually do? What if they're both at a max value (e.g 1 -> 100%)? You can't PWM more than 100% duty cycle.
