It is totally easy to get your music out there on iTunes, Amazon, Spotify, eMusic and all the rest. The trick is to submit your music professionally and have some key elements in place so you stand half a chance of breaking through the tens of thousands of musicians that will be submitting music this year. No one really knows how many songs.
1. Don't even bother submitting your music if it's not special - even special music won't sell well without good art and mastering.
2. The mix of your discreet tracks needs to be masterful with all the stops pulled out. Maximizing a track that only surfaces and then disappears in the mix is a good example there are dozens more. Another example is limiting the entire mix for best play.
3. Mastering the mix is essential so that the music plays well on near field monitors but also on cheap computer speakers, headphone, iPads, iPhones and all the other 'i's'
A critical marketing tool is to have eye-catching cover art that looks really good when it is reduced to 150X150 pixels for display on iTunes. A 1000 X 1000 pixel image at 300 DPI will look a lot different when it shrinks to iTunes size. If you are doing jewel cases, a CYMK version will need to be made. This starts running into some money, probably $1000.00 to $5000.00.
You can sell lots of CD's if you tour or have a big fan base. Otherwise you can sell your music in the DDL venues, DDL meaning digital download stores or streaming audio venues like Spotify.
If you can do your own art, website, press releases, mixing and mastering, you will be able to submit your music for about $50.00 for a CD for a net of 100% after the distributor gets paid and the DDL store gets paid. That means a $.99 download on iTunes will net you $.62. If you think that's harsh, Britney Spears at the height of her career was getting $.02 to $.06 per CD, not just a DDL song!
Don't get discouraged. New indie record labels are sprouting up to take care of your needs. They package all this work into a professional looking, released, and promoted single or CD for a percentage or no percentage for a onetime fee.
You can submit direct to the distributor too and do all the pre-submission work yourself. The Top distributor is TuneCore followed by The Orchard and CD Baby.