Update: It is best (even necessary) when your music folders/files are the same as your computer’s. Folder organization is important for the Banshee-exported playlists to “find” the music on your phone.
(I use CM 10.2 Nightlies (Franco Kernel) on LG Google Nexus 4 16 GB w/ Debian Sid GNU/Linux w/ Gnome 3 – Kernel 3.10 –> AMD64)
My favorite music player of choice is Banshee. However, it seems that it crashes whenever I have my Nexus 4 mounted. 😦
So really, the best way is to stop Banshee (that means quitting it, not just minimizing it. You have to go to the status bar and turn it off) [also, I tried w/ Rhythmbox, and it didn’t seem to play nice either…].
And, making sure MTP is turned on (by default it is, but if like me, you have had it accidentally turned off so that your phone won’t mount, go to Settings –> Storage –> USB options, or something like that). Then just open in your Files directory and go to the folder named “Music” on your Android phone. Then copy and paste Music from your computer into your phone. Somehow MTP is somewhat slower at transferring than to say a USB memory stick. I have only tried this with a rooted phone, but I assume it should work regardless. You may need to turn on USB debugging from the Developer’s Options (which can be activated by going to Settings –> About Phone –> tap it 7 times until it says you’re a developer).
A note on importing playlists: If you have any Google Play music or Amazon music, you can install from the apps. But if you have playlists you want to import from Banshee or your computer, it’s better to have all your music imported from your computer, or else your imported playlists won’t recognize the “missing” songs. This happened to me. And for importing playlists, the safest way that worked for me is to export from Banshee (when the phone isn’t plugged in, or it crashes…yes, Banshee is not the most stable software out there…but I still love it for its awesome metadata control and easy editing!) to some other location as a .m3u. Then just copy paste them into the same music folder. You may need to reboot your phone if they do not show up in Apollo or whatever app you use for music listening.
UPDATE (2013 Oct 4): If putting the playlists takes a while or does not seem to refresh or work, try stopping the app (Settings –> Apps –> Running) or (Settings –> Apps –> Running –> Show Cached). Also, if you delete the playlists in your Music folder (from File Manager or something), that will be good.
UPDATE (2013 Dec 2):
Better solution: Use SSHDroid (free from Google Play store) –> SSH in and then use scp from your computer terminal. For example, from your GNU/Linux computer, after you turn on the SSH server from SSHDroid:
scp /home/user/path-to-where-you-saved your-playlists-in-m3u-format/*.m3u root@Phone’sIPaddress:/storage/emulated/0/Music/ (Follow instructions –> input password as necessary) For me, because I exported all my playlists from banshee to my Desktop folder in .m3u format, I used the *-wildcard, so it would copy over all the .m3u playlist files found in my /home/user/Desktop/*.m3u (replace “user” as necessary or use your own filepath). Then, use the login credentials provided by SSHDroid –> in my case: email@example.com. Then follow that with semi-colon and filepath. There is only one space between scp and “/home/…” (i.e. computer filepath) and then between the “…*.m3u” and “root@IPaddress…”. I was having some problems with my playlists not listing all the songs, however. YMMV. I suggest it is still best to go via USB –> MTP.
Did I miss anything? Comment below.