A third-party software program sold to add additional function to an existing, larger software suite. An example of a plug-in is the Waves™ TDM-based plug-in audio diagnostic suite which runs under ProTools.™ There are two types of plug-in file-based and real-time. The former are usually less expensive, less powerful and require the user to wait while the effect is calculated by the computer. The plug-in modifies the data on the disk (destructive editing), but no additional hardware is required to use the plug-in. Real-time plug-ins allow the user to hear the effect while the music is playing. The real-time plug-ins require dedicated hardware to process the sound in, of course, real-time. Changes in the original file are not saved unless requested by the user (non-destructive editing.)