So, when I first got my HTC 8X I was very impressed, on taking it out with me, having uploaded no music to it, that I could still listen to all of my music on the go, courtesy of my XBox Music Pass.

Obviously, though, that's a big hit on my data plan, not to mention slightly unreliable. So before going out at the weekend I uploaded the music I wanted to listen to onto my phone. On getting onto a bus and hitting 'Play', I experienced extended delays before the music actually started to play. This has me concerned that, despite the files being on the phone itself, it was still streaming them over the air. Is WP8 clever enough to know that that track I streamed last week is now on the phone and can be played from local storage?

The only other factor which is confusing matters is that the tracks I was playing were still ones which I don't actually 'own', but ones which I'd added to My Music in the Music app on my Windows 8 PC, thus causing the tracks to be downloaded to my PC. It was those files which I copied to the phone. So it's conceivable that the delay was WP8 checking my rights to play the tracks before doing so, rather than actually streaming them. Trouble is, there's no way to know.

Finally, I tried playing back tracks from my phone which I DO own and have copied from CDs to my music collection on my PC. To my mind, these should play instantly since they are not needing to be streamed and there is no DRM (if that's still the right term) on them. But they didn't, there was a delay with them too.

Does anybody have any knowledge of such matters?