Overview of plug-in formats in Logic Pro for Mac
In Logic Pro for Mac, each channel strip has a specific channel mode, also referred to as the channel strip format. It determines the number of audio channels of the signal that runs through that channel strip. You can set the channel strip format with the Channel Mode button on a channel strip, or it can be automatically configured. See Set the channel strip input format.
In addition to the channel strip format, a plug-in also has a channel mode, referred to as the plug-in format. It determines the number of audio input channels and audio output channels of that plug-in. Plug-ins can have different plug-in formats, which are listed in the submenu when you choose a specific plug-in from the plug-in menu. The available plug-in formats depend on the channel strip format, the project surround format, and the capability of the specific plug-in itself.
Whenever you insert a plug-in, you have the option to choose one of its available plug-in formats. When you choose only the plug-in (without opening the submenu), it automatically uses the first option as the default.
Mono: The channel strip format is mono, and the plug-in is loaded as a mono plug-in.
Stereo: The channel strip format is stereo, and the plug-in is loaded as a stereo plug-in.
Mono->Stereo (or surround): The channel strip format is mono, feeding into the mono input of the plug-in. However, the output of the plug-in is stereo or surround, so it changes the channel strip format to stereo or surround from that point in the channel strip signal flow.
5.1 (or any other surround format): The channel strip format is surround, and the plug-in is capable of processing the signal natively in that surround format.
Dual Mono or Multi Mono: The channel strip format is either stereo or a multichannel format. The plug-in is loaded as multiple instances. See Multi-mono effects.
In addition to the surround master channel strip, individual channel strips in the Mixer can also be in a multichannel channel strip format. Inserting a plug-in in those channel strips requires special attention regarding the proper plug-in format.