Although it seems to be a popular concept with some people, that is a very distorted, and I believe wholly erroneous way of looking at hi-fi! Before anything else happens, the mains is transformed to whatever working voltage is desired, then it is rectified and smoothed, to create as pure DC as possible, as far as is achievable as different from the mains as it can get! Arguably it could be said that you are then modulating that DC, but it is absolutely not the mains that you are modulating. Any noise getting through the rectification and smoothing process modulates the DC and thus also the hi-fi output in some way, an undesirable effect, but that is fundamentally opposite from the music signal modulating tge nains!