Audacity is a free audio editor for online editing. It can import music and audio files of all formats and also allow you to mix, cut, delete, copy, and paste tracks to edit your files. The app also offers editing tools like volume change, pitch change, and sample rate change. And of course, you can also apply effects to your files such as noise removal, bass boost, high pass, and notch filter. You can even set the audio as a background and fade it with the envelope tool.

Audacity is also a good choice for people who want to make a podcast or a music album. You can use it to mix and combine clips and add effects to make your audio more interesting.