Jeeze. I thought the whole point of online distribution was to free the consuming public from the necessity of buying 12 songs they did not like in order to get one that they did like. Of course you can't sell a CD for $14.95 with one song on it. But if you look at the statistics, CD's are a dying market anyway. If you have a bunch of songs that can be combined into an artistic grouping in which the whole is greater than the parts, that is an album. If you have a single that does not fit with another single, that is a single. Welcome to the brave new world of digital download 45 rpm's.
As far as what online service: you are equally unlikely to make any money competing with a half million other artists of varying talent and accomplishment on any service. Even if someone were to like your stuff they are unlikely to spend 10,000 hours listening to stuff they turn out not to like before they stumble onto yours.