Audacity is a music editing program that allows you to record and tinker with audio. Not only can Audacity record audio simultaneously from various inputs (for example, a USB microphone or an electric guitar), it can also trim and edit clips. Furthermore, it supports multiple tracks, allowing you, for instance, to record lyrics and backing music separately yet at the same time.
The software also supports a number of audio effects such as noise reduction, as detailed in the extremely comprehensive Audacity manual(opens in new tab) which is both bundled with Audacity and available online. Audacity also supports VST (Virtual Studio Technology) plugins. Tracks can be exported in a number of popular sound formats such as WAV, OGG and MP3.
Audacity is simple to use and feature-rich, even when compared to much more expensive digital audio workstation software. This is a great Linux app for musicians and podcasters.