If you don't have a backup and your songs are scattered across multiple computers, you can use iCloud Music Library to unify your libraries on one computer. Here's how..
Apple's iCloud Music Library service can be ideal for you to stream content from multiple music libraries (for example, your work Mac library and your home Mac library) to a computer; Even better, you can also use it to consolidate your iTunes library if you are trying to do a manual backup.
What you should know before downloading
ICloud Music Library stores music you've purchased on any device, downloaded, or adapted from your Macs, and any subscription content you've downloaded from Apple Music. It will not store items like PDF files or full downloads of WAV files that you may have saved. If you have some of these types of files on a work computer that you are trying to consolidate in your home library, you need to manually transfer them to another Mac..
Purchased, downloaded, and paired music remains yours forever after you download it - it cannot be deleted from your library or made inapplicable. (Music purchased may authorize with your Apple ID, however.) In contrast, Apple Music subscription songs are only downloadable and playable when you have an active Apple Music subscription; Cancel your subscription and these leads are rendered inert. You can check to see which songs fall into which categories on your Mac before you download, and even organize them by type.
If your Mac's hard drive is too small to fit your entire music collection, you may need to move your iTunes library to an external hard drive..
How to download all your music on your Mac
Step 1. Choose the computer on which your canonical library is to live.
Step 2. Open iTunes .
Step 3. Make sure iCloud Music Library is enabled in iTunes> Preferences> General .
Step 4. Select Music from the drop-down menu and select the Library tab.
Step 5. Go to View> Show display options .
Step 6. Click the checkboxes next to iCloud Download.
The iCloud Download icon (cloud-shaped) tells you whether these songs are downloaded locally to your Mac or not; Otherwise, you will see a cloud with a down arrow. You can download the tracks one by one by clicking on the cloud icon, or by selecting multiple songs and clicking on them, then selecting Download.
Once everything is downloaded to your satisfaction, you can then make a backup of your iTunes Library.
Questions ?
Let us know in the comments.
