Q: i dont understand this statement "It's a good idea to keep a track that uses an Audio channel strip selected in the Arrange window, unless you're actively playing or recording to a Software Instrument."

That no longer applies in Logic Pro X 10.2.3. In older Logic versions, selecting a track with a software instrument would automatically put that instrument in "Live mode", meaning that the instrument was primed to turn any incoming MIDI into sound with a minimum of delay. This live mode makes an instrument need more CPU power (on a single CPU core) and can cause audio engine overload. This is a waste of CPU if there is no live playing. So selecting an audio track would make sure no instrument was in live mode. Now (LPX 10.2.2 and higher) live mode can be turned on or off on a track, selected or not - it is the R button on the track header.

Erik

That's the way it works in Logic 9 as well,

The only thing I see in the 10.2.1, 10.2.2 & 10.2.3 update documentation regarding "Live" tracks is this.

"An Audio preference has been added for multithreading live tracks to improve CPU performance when processing multiple live channels."