That I guess would depend on the persons musical background. What would take me years, a good musician could probably master in a couple of days.

That aside, I have these personal rules for doing anything.

To be able to do something, you must practice (or train) at least ten minutes a day.

To be able to do something WELL, you must practice at least two hours a day.

To be able to do something PROFESSIONALLY, you must practice at least eight hours a day.

FWIW, Bert.