Why doesn't the Mixer Toolbar input selector work properly, for example on Windows Vista?
The Input selector may be greyed-out, lacking the expected choices, or apparently not recording from the indicated source.
The cause varies by operating system and sound card driver. For example, on Windows Vista, you must use the "Recording Device" menu in the Audio I/O tab of Preferences to select input sources. For more help, see the Mixer Toolbar Issues page on the Audacity Wiki.

