My band director switched me from trumpet to french horn two days ago, and I was wondering if it was bad to have my mouthpiece off center. I played trumpet that way, and I was wondering if I could do the same while playing French horn. I know that you're supposed to have it in the middle of your lips, with more on the upper lip, but could I continue playing with the mouthpiece on the left side of my mouth? Thanks.

I've seen people play [trumpet] out the side of their mouth just fine. As long as it sounds good and isn't damaging your lips/teeth, then I wouldn't worry about it much.

Of course, having the mouthpiece nearer the center of your lips helps with airflow, and french horn requires a bit more air than trumpet. So, if you have the wherewithal to correct it, I recommend attempting to do so before you get too far along on french horn. Doing it right when you switch rather than waiting a couple weeks/months will really help your habits if you plan to play longer than just a few years.

"Is playing on the side of my mouth bad?"

Probably. It makes the muscles work in a lop-sided (and therefore inefficient) way. You can get away with being a teeny bit off-centre, for example, if there is a problem with your teeth, but I would be looking at getting my teeth sorted out in that case.

"If it works, it's correct"

Valerie Wells
http://beforhorn.blogspot.com/
http://comfyhornstrap.blogspot.com/