I want to record the audio from my computer, meaning if I play a youtube video or something else(like a video), I’d like it to make an mp3 of the audio. I know you can extract the audio from youtube videos, but I really would like to try just keeping the audio that is playing.
Don’t get too lost in all the options. Install it, click the big red record button, start your video, when it’s done, click “stop.” If you want, trim the beginning and the ending. Export or save as* MP3.
I go back and forth between two versions, and I can’t remember right now what the current option is.
As a general discussion about recording sound off of your computer (and completely ignoring where you are getting the audio from so that we avoid discussing copyright issues), let me just say that on many computers, the sound card’s output does not show up a a device for recording. However, in Audacity, you can generally select Windows WASAPI for your recording interface, which will record whatever is coming out of your sound card.
Everything that’s been said thus far about Audacity, I can +1.
And while that’s a swell way to capture your soundcard output, if you have video files that you’ve downloaded (or that got onto your PC some other way) and you want to extract the audio, try Pazera Free Audio Extractor. It’s freeware, and I’ve been using it for maybe a decade with excellent results. There are a bunch of other freeware Pazera conversion tools, too; I can’t explicitly vouch for those, but my guess would be that they’re also nifty and hassle-free. (WinPC only; sorry, Mac folk. Linux people: runs fine under Wine, I’m told.)
For simple video editing, conversion, and audio extraction, Avidemux (free and open source) is pretty good. Despite its name, it handles dozens of video and audio formats, and will do most kinds of conversion, cropping, resizing, filtering, rotating, etc. Simple and fast.
… and VLC (free, open-source, available for almost any platform) can not only play almost any media file you throw at it (including podcasts), it can record and convert almost anything to almost anything else.
This script will save a copy of a YouTube video on your local system. No sound card involved. There is also a youtube downloader browser plug-in if you prefer. You may then use VLC, Audacity, or anything similar to extract the audio track. Conversion to mp3 is straightforward, but I wouldn’t bother if the audio is already compressed, possibly with a more complex codec.
[IMHO / this is not legal advice part:] Respecting any hypothetical copyright/license notice is your responsibility, of course, but people watch and cache videos and music on their devices all the time, so unless you plan on doing something blatantly egregious (like including the ripped music in a commercial DJ set or using samples in your own composition) there is zero chance you’re going to get sued for downloading a YouTube video.