Several people have asked me about the audio quality of the dementia-friendly music player, given that it uses a Raspberry Pi. Raspberry Pis are known for good but not great audio quality from the built-in headphone jack. But you can now get really good audio quality from the Pi's built-in headphone jack. You need an experimental firmware update from the Pi Foundation, see this raspberrypi.org thread. Or see how I built the software image for the dementia-friendly music player. Prior versions of the Dementia-friendly Music Player used a USB audio adapter. And the very first version used a rather expensive external USB audio adapter with an integrated headphone amplifier. But it's really hard to hear the differences between those three versions. So the current version just uses the built-in headphone jack. In other words, the firmware update is pretty darn effective. It's an experimental firmware update, but for my limited purposes it's been wonderfully reliable. The firmware update works with the Pi A+, Pi 2, and Pi 3.
I should also note that the Dementia-friendly Music Player supports MP3, AAC/iTunes, FLAC, and Ogg Vorbis music files.