Gsm files instead mp3 files in a conference room!

I want to asterisk play gsm files instead mp3 files when only one person is in a conference room with ‘M’ option in Meetme application.Is it possible?
(I place 2 gsm files in mohmp3 folder and didn’t install mpg123)
I’d appreciate any help.

change musiconhold.conf
instead of quietmp3 to file