Is it a bad habit to use an electronic tuner while practicing an instrument in which the notes are not fixed after tuning (e.g. violin, trombone)?
I'm asking because I've heard a lot of people say that it's a bad idea because you are using visual feedback when instead you should be hearing whether you are in or out of tune. I understand that in the ideal case you would have a good ear and be able to tell whether you are "too high" or "too low" and adjust accordingly, but the reality is that a beginner usually doesn't have that developed ear and won't be able to tell. This results in the student practicing and learning a piece at home incorrectly without knowing all along that it was wrong. Wouldn't it be more harmful to get used to hearing the wrong notes while practicing?
During class the teacher is there to correct this and many other issues that he might notice as he watches the student play, but at home the student doesn't have any feedback as to whether he is practicing correctly or not.
What should be done in this case when the student just can't trust their ear because it's not developed enough? I'm sure there must be a better solution than a tuner since great instrumentalists have been playing "in tune" for centuries without these devices, but I can't help but think that some kind of feedback is useful.
What would you recommend if it was your student?