I blogged this recently:

Selling Music Online - the Minimal Way

A friend of mine called me yesterday while I was standing on the end of the Santa Monica Pier saying that one of his band's songs would be airing on Grey's Anatomy next Monday. He asked how he could quickly setup his website to be able to sell an MP3 of the track in time for the airing. The band already has a paypal merchant account and this would be only need to be a temporary solution.

I thought about the question and asked a few technically inclined musician friends about their experiences. (Neither of which were very helpful! One recommended an "online" music label and the other warned of RIAA restrictions.)

So, here's what I came up with and recommended to my friend:

1. The simplest (but most insecure) way to sell a track online is to simply edit the PayPal "Thank You" page on the site to include a link to the track. Basically what will happen is when someone buys something from your website, they click the "add to cart" button which takes them to the PayPal shopping cart where they fill in their billing information and buy. Once the transaction is complete, PayPal sends the customer back to a "thank you" page on their server. So, by changing that page to include a link to the track they can download it. (Now, I'm not sure how this would work if they bought a tee shirt or something else. - maybe they'd just get the mp3 for free in that case?) Anyway, the issue with this is that they can copy the link to that thank you page and give it to their friends who can then go to that page and download it all they want. (Probably not a huge deal at this level, but they may lose sales.)
   
   
2. So, there seems to be other people out there who want to do the same thing and there are several services that help out by simplifying and securing this process by providing an easy way to restrict the downloading of the track to only those who purchased it through PayPal. (The two listed below simply work with your existing PayPal account.) It looks like it would be pretty cheap to use either of these setups. (Actually they both offer either 1 week or 1 month free which might be enough time in my friend's case!)
   
   These two services allow you to upload the digital files you wish to sell to their server and enter you PayPal account information. They'll then accept the "Buy" button links from your website and pass them off to PayPal's standard interface for payment. PayPal then returns to their site for the "Thank You" page and a secure, limited time download URL is provided to the purchaser.
   

• EJunkie (Pricing)
• PayLoadz and PayLoadz Express (Pricing)
  
  Simple, straightforward and to the point!
  

An Additional Note:

From my reading, PayPal now has new rates for micropayments which cost less for items under $12. (5% + $0.05 vs the standard 2.9% + $0.30) See PayPal's Site for more information on micropayments.

So, without knowing more about the subject, I think one of these services would be the way to go. They both look like they are pretty easy to setup and the deciding factor would simply be cost projections based on how many sales they expect to make! Good luck guys!