Legacy: Can Audacity record RealAudio or other streaming audio?

Windows and Linux
With most Windows and Linux audio devices, it is possible to record whatever sound the computer is currently playing, including internet radio streams.

In the drop-down menu on Audacity's Device Toolbar, choose “Wave Out” or “Stereo Mix” as the input source. (The exact name may be different, depending on your computer's sound drivers). On Windows, if you don't have a “Wave Out” or “Stereo Mix” option, or if it won't record, go to the system Control Panel and try to enable this option there. For instructions see: Using the Control Panel.

If this doesn't work on your computer, you can instead use a cable to connect your computer's “Line Out” (speaker) port to its “Line In” port, and use Audacity to record from Line In.

Note: Do not enable "software playthrough" when recording computer playback, because this creates a series of echoes.

Mac OS X
Mac OS X users can capture streaming audio using a program like Soundflower (free, open source), Audio Hijack or Wiretap Pro. For more help see this page.