How to transfer music from iPhone to computer?

Have you ever come across one of the following problems when using iPhone?

I bought a new iPhone and all my songs are stored in the old computer. Is there any way I can use to transfer those music files from my iPhone to the new computer directly?
My computer crashed and I have to reinstall the operating system. My music files and films are deleted via this process. Is it possible to transfer music and movies from iPhone back to computer?

Guide: Transfer music from iPhone to computer step by step

Tools Required:

iPhone to Computer Transfer - A backup software for iPhone users to copy files such as songs, movies, and photos from iPhone to computer or iTunes library.
iPhone to Mac Transfer - For Mac users
USB cable

Step 1: Download and install the iPhone software. Launch it.

Step 2: Connect iPhone to computer via USB cable.

Connect iPhone to computer

Step 3: Select and check music files from "Audio" node or from a Playlist you want to copy.

Step 4: Click "Export checked files to local" button start to transfer music from iPhone to your computer hard drive.

Transfer iPhone to computer

Tip: If you want to copy files to iTunes library, just click "Export checked files to iTunes library" button.

OK, done.