Analog modem has a maximum download rate of 53.3 kbit/s. There are 19 genres of music on FM radio: Jazz, Adult Album Alternative, Top-40, Spanish Pop, Ethnic, Hot AC, Rock, Country, Religious, Hot AC, Classic Rock, Rock, Spanish Pop, Christian Contemporary, Hip Hop, Tropical, Adult Contemporary, Christian Contemporary, Urban Contemporary,
and 2 on AM radio: Spanish Christian, and Gospel Music.
What we really needed was an audio codec (XM uses HE-AAC, HD radio uses PAC) that got the best sound possible at whatever AM can broadcast at, which according to the wikipedia is 40 kbps, and then emphasized multicasting for FM so that more genres can be available in more locations. The biggest market is NYC.
The thing is, I think the technology was launched before it was ready, there is now HE-AAC-PS which should sound superior at 40 kbps. Then there's the AMBE codec that I'm not sure can go to bit rates that high.
And I would also point out - there is Music Choice on HDTV. Why not have the genres reflect radio genres so we don't hear "Jet Airliner" over and over again?