Two way sync with rsync

Since the original question also involves a desktop and laptop and example involving music files (hence he's probably using a GUI), I'd also mention one of the best bi-directional, multi-platform, free and open source programs to date: FreeFileSync.

It's GUI based, very fast and intuitive, comes with filtering and many other options, including the ability to remote connect, to view and interactively manage "collisions" (in example, files with similar timestamps) and to switch between bidirectional transfer, mirroring and so on.

FreeFileSync can easily sync two computers on the same network and also sync two computers on different and remote networks.

• On same network: have FreeFileSync use the local file system on one side and a shared network drive / path on the other. On Windows systems you enable file / disk sharing on one computer and access that share from the other. I use FreeFileSync this way to keep my main development PC source code synced with my 2 laptops. I have also synced one of these laptops with a Linux server with Samba installed and sharing one of its directories.
• Across networks: create a VPN and do the same as above. FreeFileSync will see the remote disk as it was on the local network. Or buy one router that allows you to connect a USB disk to it and share over the internet. I have installed a VPN on a remote Linux server and used it through the OpenVPN Windows client.

You could also try bitpocket: https://github.com/sickill/bitpocket

Try Unison: http://www.cis.upenn.edu/~bcpierce/unison/

Syntax:

unison dirA/ dirB/

Unison asks what to do when files are different, but you can automate the process by using the following which accepts default (nonconflicting) options:

unison -auto dirA/ dirB/

unison -batch dirA/ dirB/ asks no questions at all, and writes to output how many files were ignored (because they conflicted).

Note: I am no longer using Unison (I use NextCloud, which doesn't address the original use case). However, note that rsync is not designed for bidirectional sync, while unison is. unison may have its bugs (as any other piece of software) and its wrinkles. I am surprised it seems to be actively maintained now (last time I looked I think I thought it looked dead), but I'm not sure what's the state nowadays. I haven't had the need to have a two-way file synchronizer, so there may be better options, though.