The Bach 36B Professional Medium-Large Bore Tenor Trombone The Original Possibly the horn that started it all. This series of instruments was developed to bridge the gap between the very small bore tenor trombone without going to the full symphonic size. The modest bore and the various options available make this an excellent all around instrument for the serious player. The ease of playing is basically unmatched by other instruments. We feel you will find this to be a very good choice.