iPad Distortion?

[Paul-sings]

I'm a musician who uses backing tracks on an app called OnSong (which is a digital songbook that instantly pulls the track from iTunes and provides a play button on the bottom of the chart, highly recommended). Recently I upgraded to a much newer iPad from a 3rd generation. Sometimes when i'm playing, I'll have rather loud static, like a scratchy distortion sound at the start of the track, as if it was recorded very hot. This happens on some songs I've been playing (problem free) for years. I have an old MacMini. Any ideas?
Definitely not cables, the mixer or the speakers...all high quality and new.