Seattle's own excellent public radio station, KEXP, has a very informative article by John Richards called Working Towards Radio AirPlay which offers many suggestions about how indie musicians can get their music played on the radio. I have one issue with it, however, and that has to do how to get your album to a station in order for them to consider playing it. (I'm sure he's just telling it like it is--or was in 2011 when the article was published--but I really think it should be different.)
He does advocate sending a hard copy of your album, even if you have sent a stream.
Media formats are constantly evolving. I get music files and streams on a daily basis. It works the same way as records for me. For instance, I recently got the new M83 single sent to me and it hasn’t been on the radio yet. Did I go right to the file and listen? Hell yes — I know M83 is a great band. Was I rewarded by doing this? Hell yes — it sounded great. Now imagine all the other emails I’m getting as well, which are a lot. That’s the nature of the job but you have to remember that. What most stations have is a “MD”, which isn’t a doctor of airplay but a “Music Director”. If you’re a small band, new band, whatever, it’s going to be hard to get their attention. Send it but make sure you let the MD know why they should listen to you and if possible, send a hard copy as well. With a DJ you should do the same. The worse they can do is ignore you. We still have plenty of stations that use CD players.
CDs can be very expensive in small runs. Then there's the time and the postage to get it into the mail. Worst of all, since most of songs being sent in will never be chosen to be played on air, it's a total waste of plastic. My preference would be to send digital FLAC or WAV files, or a physical CD if the station requests it after listening to all or part of the album in a digital stream.
It's great that we live at a time when it's so easy, cheap and environmentally friendly to get your music to a station.