With PlayPASS Music Player, you can instantly download and play purchased CDs, DVDs, and Blu-rays. No need to transfer them from your computer! It’s also a free music player that you can use every day, allowing you to download and play music purchased from participating stores.
A PlayPASS code is a free code that allows you to download music and videos from purchased CDs/DVDs/Blu-rays. It is included with PlayPASS-compatible CDs/DVDs/Blu-rays. Use this code to download music for free.
AFAIK it’s not DRM-free, so you still have to rip your discs for FLAC/MKV but it’s still a neat thing to be able to have a copy for your phone (or 3DS)