To cut audio files fast, there are 3 ways to do it.
First is online, this site:http://mp3cut.net/ is very easy to use, but there are problems like network and file size.

Second way is to use VLC player,
1. Add music and click "Advanced Controls " in the View item and a red record function will shown.
2. To play music first, to click the red button to start recording, to end recording, you just need to click it again.
3. Just find your created file in your computer.

Third way to cut audio files is using some third party software, like the Handbrake.

Very useful