I have been experimenting playing .wav files on loop while moving objects around the screen and notice a real lag on the iPhone simulator. It seems a little better in the iPad retina simulator.
@dave duke mentioned an issue playing background music in his Pixel-space-war app and that the Xojo team were looking into it. I have been checking but haven’t seen anything further about the fix.
Try using the AAC codec instead and lower the samplerate to 22050Hz and a bitrate around 128kbs or even 96kbs. Avoid 5.1 and only use stereo or mono.
On an iPad and iPhone this will still sound very good but will have less strain on the cpu.
For anyone in the future: Check out https://forum.xojo.com/37906-avoider-game-code which has a solution to this problem with declares.