Audio power efficiency idea.

Normally Linear amplifiers lose a lot of power into heat.

What are the possibilities of using a switching FET output to recreate the apparent audio signal?
Say, run the switching PWM FET @ around 48Khz and create an LCR crossover which act as a low pass pi filter to reproduce the apparent linear audio waveform to drive the speaker coils?

CDs rebuild audio from PCM already at 44.1Khz data encoding.

Might be a nice experment to try.

EDIT: Seems to have been done already.
https://www.electro-tech-online.com/custompdfs/2003/09/AN1042-DPDF.pdf

Yes, it's been done many times. You can buy audio power ICs that use Class D (switching) outputs to get high efficiency. They're often used in battery powered audio amplifiers to maximize battery life.

Texas Instruments have a few excellent class-D audio power amplifier ICs. They switch at a very high frequency so that the output filter works well.
They are so efficient that a fairly high output power requires no heatsink on the IC.