If you know any DSi Secrets post them here.
Heres some you probably know but might not know--

Go on DSi Sound and go to where the bubbles are, and leave your cursor on one of the bubbles for about a minute, it will play mario theme song

Hold select and use volume control to change brightness ingame.

Hold L and R and Select and Start and then press power button (Dont hold it) to go to calibration ingame

Hold L and R and start and select and dont press power button to restart game

This ones kinda complicated in a way, go online and type in "DSi Piano Grid" and u will get a picture of a grid with a bunch of notes. Take the picture perfectly aligned with the DSi camera, then go on DSi camera and click view album. go to the picture, and click edit. then go to the writing thing where u draw stuff, clear it, and go to stamps. Click the little music thingy, and click anywhere on the grid, and wherever you click, it will play that note. (For more detailed instructions look this up online.)

And last, theres little minigames u can play on DSi Sound when u have songs on ur sd card, just press down on D-pad or pull string and press L and R to play games

Hope this was helpful Post any more in the comments if you no anymore xP