Finder aliases are soft symlinks. Some programs do not or cannot follow them. Symlinks created with the ln command are hard symlinks and are fully able to present themselves as folders or files to everything that requests them.
Correct, except that the "everything" bit. Unfortunately iTunes is not able to fully follow them.
I've played with the idea of splitting up my iTunes library using symbolic links. I wanted the media info (stuff like album artwork), Books and Mobile Applications to remain on the SSD and then move the individual folders like Music, Movies, iTunesU and TV Shows to the second HDD.
This works for playback, but it goes wonky if you download extra stuff. Basically iTunes won't follow the symlink if you download a movie and the file will not be moved into the correct directory. It will remain in the downloads folder.
Also if you tick "Keep media organised" and then add an item to the library manually, it also won't follow the symlink and stick that item into the correct directory. For some strange reason iTunes uses an odd method in the code to do this that is not compatible with symbolic links. There are plenty of discussions on the net about this, which I only found after trying to do this.
In the end I moved the entire library from the iTunes level to the second HDD and created a symbolic link called iTunes in the home/Music folder.
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Ahh, ok i thought an alias was exactly a symlink as created by
ln -s. I learned something new today!
Apart from what was already mentioned, an alias is a lot larger ( a couple of megabytes vs a couple of kilobytes) and also an alias keeps track of what it is pointing to. So if you're pointing to a file and then you move it or rename it, the alias will continue to work. The symbolic link will no longer work and will need to be recreated to point at the new location.
OP: copy the music folder to your other HDD. Create a symbolic link to it in your home drive called Music. Your sidebar buttons will continue to work because they are actually aliases.
For example: if I move my Documents folder to somewhere else or rename it, the sidebar buttons will still work. But you still need to create a symbolic link to Documents in your home folder to make sure all other applications work as expected. I hope that makes sense.