The familiar tape cassette was designed to accommodate four channels of audio – in a commercially recorded cassette these four tracks would normally constitute the stereo channels (each consisting of two tracks) for both 'sides' of the cassette – in a four-track cassette recorder all four tracks of a cassette are used together, often with the tape running at twice the normal speed (3¾ instead of 1⅞ inches per second) for increased fidelity. A separate signal can be recorded on to each of four tracks. (As such, the four-track machine does not use the two separate sides of the cassette in the conventional sense; if the cassette is inserted the other way round, all four tracks play in reverse.) As with professional machines, two or more tracks can be bounced down to one. When recording is complete, the volume level of each track is optimized, electronic effects such as reverb are added to certain tracks where desired, each track is separately 'panned' to the desired point in the stereo field and the resulting stereo signal is mixed down to a separate stereo machine (such as a conventional cassette recorder).