How do you put music on a sandisk sd card?

Music can be placed on any area of the SD card, best practice is to put it in its own folder, usually labeled 'Music' The DSi can read up to 8 folders deep for music, and can display up to 1000 Music files at a time. The DSi plays music files of the AAC format. These music files usually have the .mp4 .m4a or .3gp extensions. In most cases you will need to convert a music file for use. I suggest using the convert/save feature of the free open source software VLC player (Video Lan Player).