From Logic Studio Training Wiki
You can add software instruments to your project in several ways:
- Use the Track > New... menu item in the Arrange Window's toolbar and choose Software Instrument.
- Use the Library to insert an instrument and its effects into a track's channel strip.
- Choose a channel strip setting from the track's inspector by click-holding the channel strip's Setting button.
- Choose an instrument by click-holding the instrument slot in a track's inspector.