On Mac OS X, what if “sound play error -2004” is reported?
This isn’t really a frequent problem, but it has been reported twice. This mysterious solution was reported (by both people) to succeed: go to the Applications folder, and then the Utilities folder, and run the Audio MIDI Setup application. Under “Audio Devices”, “Properties For: Built-in Audio”, “Audio Output”, in the lower right, reduce the “Format” setting to 48000 or less. The default value is 44100.0 Hz on at least one computer; click here for a picture of its settings.