ho trovato una "possibile" soluzione, dato che sembra appurato che il problema sia in El Capitan.

eccola:
Only the last version of Logic 9 (9.1.8) has a chance of running on El Capitan but the fact is... Logic-9's built in graphic routines are now pretty much outdated, in Apple's most recent operating system. It's only going to get worse.
If you're on a MacBook Pro that has graphic switching (hardware/software) turn off Graphics switching is System Preferences (probably under Display) this will force the computer to use hardware all of the time.

Qualcuno ha testato la soluzione ?
io non avendo un MacBook ma un Mac Pro "desktop" non ho la spunta da fare in System Preferences

idee, soluzioni ?
grazie