A plug-in is software you add to a DAW to extend its features. Some process audio, like EQ and reverb; some are instruments that turn MIDI into sound; some transform MIDI data. Certain plug-ins ship with the DAW, while others are installed separately.
Three main types
Audio effects process incoming audio with EQ, delay and so on. Instrument plug-ins receive MIDI and output audio. MIDI effects, such as arpeggiators, process note and controller data. Because they handle different signals, the tracks they go on and their position in the chain differ too.
Order changes the result
In a channel strip’s inserts, the signal generally passes through the plug-ins from top to bottom. Placing an EQ before or after a compressor, or sharing a reverb on a send, gives different results depending on order and routing. Audio effects normally go after the instrument.
Formats and compatibility
Plug-ins come in formats such as VST, Audio Units and AAX, and your DAW and OS must support the one you use. Even within the same format, a plug-in may fail to load depending on the CPU type, the OS and the plug-in version. Check the supported environment and the license terms before installing.
CPU load and latency
Plug-ins that use high-quality processing or look-ahead can increase CPU load and latency. Delay compensation in the DAW keeps playback aligned, but monitoring while recording is still affected. Heavy processing can also be committed to audio by freezing or bouncing.
Troubleshooting checks
If a plug-in is not recognized, crashes at startup or makes no sound, check the format, the scan state, the license, the inputs and outputs, and where it is inserted, in that order. Avoid adding many new plug-ins at once so you can isolate the cause. For plug-ins Logic Pro does not recognize, see How to Rescan Plug-ins (Japanese).
