Most of the time throughout this book, we haven't paid any attention to supporting older Android devices, the main reason being that all the up-to-date parts of the API we have been using work on such a high percentage of devices (in excess of 95%) that it has not seemed worthwhile. Unless you intend to carve out a niche in apps for ancient Android relics, this seems like a sensible approach. In regard to playing of sounds, however, there have been some relatively recent modifications to the Android API.
Actually, this isn't immediately a big deal because devices that are newer than this can still use the old parts of the API. But it is good practice to specifically handle these differences in compatibility, because eventually, one day, the older parts might not work on newer versions of Android.
The main reason for discussing this here and now is that the slight differences in pre- and post-Android Lollipop sound handling gives us a good excuse to see...