I have a bunch of FLAC files from an album I bought, it was that or low-quality MP3. iTunes ("Music.app") doesn't read FLAC, even tho it's the industry standard for lossless audio.
So I fought with ffmpeg (each "f" stands for "fuck you"), and it converted about half of them into usable files.
Eventually I found XLD X Lossless Decoder: Lossless audio decoder for Mac OS X
Had to right-click, Open to get past Mac Gatekeeper, ugly little program, been in development forever, but it works perfectly. Converted a directory full of flac into m4a, then just dragged them into iTunes and now have music where I want it. If I'm real excited for it, I could downgrade them to AACs, but eh good enough for now.
Everyone be sure to tell Apple that ALAC is stupid and not going to happen.
(the ffmpeg I did was:
for f in *.flac; do
echo "$f"
ffmpeg -i "$f" -c:a alac -c:v copy -acodec alac "${f%.flac}.m4a"
done
but now I really don't wanna hear about how to fix that.)