Garageband freezes on "Optimizing performance" iPhone 6

Is there any way around this problem? Every time I open Garageband & pull up my song, it immediately goes to "Optimizing performance", gets about 75% done, then freezes (for as long as 3 hours before I gave up).

I have tried the following:

-Close all other apps

-Reboot iphone

-Hard reboot iPhone (hold down Home & Off buttons)

-Pray to the gods of mount olympus