SM is the evolution of radio.

First, there was AM, which offered muddy sound and static and you had to be near a radio to listen.

Then, there was FM, which was less muddy with less static, but you still had to be near a radio to listen.

Then came XM, which was crystal clear (as long as you weren’t in a building or under an overpass. But, you had to PAY to listen to music.

Now, there is SM, streaming media which you can listen to for FREE with crystal clear sound wherever you have an internet connection.