Audacity is a cross-platform, free program for recording and editing sound. You can use it to record live audio or to edit existing recordings. The website has a comprehensive help guide and the software is easy to use yet powerful enough to edit and produce good quality results.
There are various effects to improve the audio quality – fade ins, equalization, compression and normalization – and comprehensive edit tools that allow you to cut, copy, paste, move, and insert audio across several tracks if needed. There are other tools to improve other media types – vinyl and tape etc. There are also some music creation effects.