Why is it illegal to download music off the internet but not record a song radio?

It is not illegal to download music off the internet. It is illegal to download music without the permission of the copyright holder, but there are many legal ways to download music, such as purchasing it from an online store or streaming it through a subscription service.

Recording a song from the radio is also not illegal, as long as it is for personal use. However, it is illegal to distribute or sell a recording of a copyrighted song without the permission of the copyright holder.