Digital Radio Mondiale (DRM) is already widely used on medium wave and short wave bands. It uses QAM, a kind of AM and broadcasts in stereo with a HTML information stream. You can't hear it on a normal AM radio, it sounds like a slight rise in background noise but it is quite easy to decode using simple hardware and a computer to decode the data stream.
FM radio sounds much better than AM radio. FM radios play up to 15kHz but AM radios are muffled up to only 3kHz to 4kHz. FM radios suppress background noises but AM radios play all kinds of clicks and pops caused by lightning or any other Amplitude interference. AM radios can play two or more stations at the same time but FM radios do not (a good capture ratio).