Imagine having your entire collection of music (including high resolution 24 bit files) available to you in your Tesla.
I would like to personally recommend TeslaTunes. I converted from ALAC to FLAC the old fashioned way (manually with XLD) and it took me over a week of babysitting the process (I have 50,000 songs). It's also complicated by having aac and mp3 files that DON'T need to be converted and you have to filter those out by creating smart playlists, etc...
With TeslaTunes, you just choose your options and let it do the rest. It takes about a day for my collection but I have many hi resolution files (24 bit) that take a little longer. I dump them on a 2 TB drive and plug this into the USB port. I hide the drive behind my center console in the back.
I wish Tesla would support Apple Lossless (ALAC) as it is open source but TeslaTunes makes it easy to convert. I'm sure it's on their "to do" list at a very low priority.