The 36 Series Professional Trombone The Value of a Medium Bore Horn The 36 series Stadivarius instruments are the standard that other companies are trying to match in their product line offerings. The 36 has one of the more beautiful, singing sounds in the industry. The medium bore makes it fun to play under any circumstances and wont make you work too hard in the process. So if endurance is a concern, this is the horn for you.