In today's Japanese Nintendo Direct conference, Nintendo announced a brand new Music player and online store for Nintendo 3DS...
The new 3DS application will allow you to purchase music from an online store, much like Apple's iTunes. The service is confirmed for Japan, but there is no information regarding a global launch of the service. But it does look pretty awesome!
Source:
http://www.nintendofansonline.co.uk/2012/10/news-nintendos-equivalent-to-itunes-is.html