Apple Logic Express 7 - Manual (Page 20)

20 Chapter 2 Instruments and Effects
Bus Effects
When you use bus effects, a controlled amount of the signal is sent to the effect. Buses
are typically used for effects that you want to apply to several signals at the same time.
Within Logic, the effect is placed in an insert slot of a bus object. The signals of the
individual tracks can each be sent to the bus, controlled by a Send knob.
The audio signal is then processed with the effect, and mixed with the stereo output.
The advantage of this “bussed” approach, over inserting effects on tracks, is efficiency.
This method allows as many tracks as you like to be processed by one inserted plug-in,
massively saving CPU power when compared to insertion of the same effect directly
into multiple tracks.
For computationally-intensive effects such as reverb, it’s always advisable to insert
them into a bus. Chorus, Flanger, and Delay effects should also always be inserted into
a bus, if they are going to be used on more than one track.
In some cases, it may make sense to patch an effect such as a delay, directly into the
insert of an individual track. There are no restrictions in Logic as to where effects may
be used.
Instrument Plug-ins
The Audio Instrument Object Type
Unlike effect plug-ins, instrument plug-ins respond to MIDI note messages. Instrument
plug-ins can only be inserted into special Audio Objects, called Audio Instruments.
Audio Instruments feature a special instrument slot, directly above their Output slot.
An Audio Instrument is an Audio Object with its Channel parameter switched to one of
the Instruments. Any audio object can be switched to operate as an Audio Instrument,
by changing this parameter (Channel) in the Object Parameter box.
To create an Audio Instrument Object:
1 Open Logic’s Audio Mixer, by choosing Audio > Audio Mixer.
2 In the Audio mixer window select New > Audio Object to create a new Audio Object.