I have an old 10.6.8 version Mac OX S and am using similarly antiquated n-track version 2.2.2 - that’s a far as this Mac can go. Once I have recorded a track, and I attempt to free-play an additional track from a synth or guitar/bass through a preamp, the output from the device (synth, guitar) has a lag, making it quite impossible to do. I can’t figure out how to hear the instrument in real time, in sync with the previously recorded track, that accurately corresponds to hitting the piano key or the guitar string. (?) 
Would appreciate any help. Thanks. ~Lefty7
On Mac you can typically use very low buffering which should make latency so low as to not be hearable. Try lowering the buffering settings in the Settings -> Buffering box, try for example 2x256 or 2x512.
Alternatively you can use larger buffering but disable real-time monitoring via n-Track, so that when you record you only hear the instrument via an analog connection. The recording should still be in sync.
Regards,
Flavio.
Thanks, Flavio. 2x256 cut the LIVE monitoring lag way down, and if I had been putting on some legato strings or something, it would have been fine, but I was slipping in little brushes-on-snare-drum syncopated phrases; the timing was so close that even that slight lag was still an issue. Taking your suggestion a little farther, I went to a custom dithering setting of hyper-low 64, and that erased the lag to my ear, and I was easily able to go forward with that and other parts as well. Thanks very much. 
~Lefty7
That is to say: a custom buffering setting of hyper-low 64. 
~Lefty7