I think you can! Or not.
Use a converter website that you can find songs on
Find a video converter online or you can use really player.
pandora.com
Itun
yes, but if you find something on youtube that you like you can go to YouTube to mp3 Converter. org and follow the instructions
If you search on google for "youtube to mp3 converter" you will find various programs to convert youtube videos to mp3. Try some of them and see which one works for you. You can find a lot of music on youtube.
What you have to do is find the right converter that will convert a mp3 file into a mp4 file. It might take a few tries to find the right one. Then load the mp3 files you want onto a memory stick. Then go on the converter, add the mp3 file and select destination as sd card (You can't do it without an sd card) then convert it and load the sd card into the slot on your nintendo. Press Dsi sound then click "play with your music" select the song you want to play. You can change speed and pitch of your songs and more.
== == == ==
musicnotes.com
Music-wise, jailbreaking does not get you any free music that you wouldnt have had without jailbreaking it. You can find free music anywhere online, with or without a jailbreak. Jailbreaking does not get you free music, but does get you mods, apps, etc.
From a music store? If you want that online without paying, that's illegal.
You can google it , the keyword is 'amv converter '.