Hm, sounds like you need to see directly with Algoriddm's support people.
For me it looks like the app took your tracks from the Music app and moved them to the App's player instead. Might also be possible that the two apps could not operate together - try ending the Algoriddm on by double-pressing the Home button then tap and hold the app icon until you see the Minus sign. Tap on the minus sign.
Does that fix anything?