How to back up from iTunes library to iCloud. This is new service from Apple on iTunes 12.
This is complete guide "How to back up to iCloud with iTunes 12".


Getting Started
To subscribe to iTunes Match:
1. Install official iTunes 12 on your Mac
2. Open iTunes and choose Turn On iTunes Match from the Store menu
3. Click the Subscribe for $24.99 button and follow the onscreen instructions. Once
complete, your Music library will include songs on your computer and in iCloud.

Once iTunes has completed matching your music with the iTunes Store, you may begin
accessing your iCloud library:

• From your iOS device:
1. Tap Settings > Music > turn iTunes Match ON.
This will disable syncing music with iTunes.
2. Press the Home button and tap Music.

• From your other computers:
1. Install iTunes 12 on your other Macs
2. Open iTunes and choose Store > Sign In. Sign in using the same Apple ID you used
to subscribe to iTunes Match.
3. Choose Store > Turn On iTunes Match
4. Click the Add This Computer button
5. Once complete, your Music library will include songs on your computer and in
iCloud.

Mmmm. Cool.
We Wait official release iTunes 13 from Apple with new features.