Is it possible to change pitch (multiply/divide) or frequency (add/subtract) to audio files while they play

[Winston]

I looked for code that changes the pitch of sound, even with speed, but none of the code I found online works. How would I program a page to have that ability? We already have volume, and speed, but pitch or frequency is refusing, and I wonder if old browsers had it, but was discontinued...? People on other Forums are ASKING THIS SAME QUESTION, and they DID GET CODE; THAT DOESN'T WORK ON MY COMPUTER! So what is the WORKING code?

[Ingolme]

Pitch control is not one of the default controls of the <audio> element, so any code which can do it will be complicated.

The Web Audio API is a powerful tool for generating and manipulating audio signals, but it is complicated. I can't just give you code to use because it would take a few hours of my time. The BiquadFilterNode should be able to alter the pitch of a signal passing through it.

[Winston]

So I ran into a problem... When I try to edit the code to change the frequency of sound in https://mdn.github.io/voice-change-o-matic/ , the webapp does nothing. I tried something like;

biquadFilter.frequency(2000);

To increase it by 2000Hz. Am I missing something, do I need to get and set frequencies? How, if so?

"Because reverse is slower than forward; reverse is below stopping time." (Yes, I made up that quote. Do you like it?)