An improved mouthpiece for use with single reed woodwind instruments is provided. The mouthpiece includes rounded portions of the top surfaces of the side rails and tip rail that surround a window of the mouthpiece that leads to an internal tone chamber. The rounded surfaces reduce turbulence in the air flow during the reed closure segment of the oscillatory cycle, improving tonality, response and intonation. The mouthpiece also includes a step or raised portion in the table portion of the mouthpiece adjacent the window. The step elevates the heel end of the reed. The raised heel end permits increased vibration of the heel end of the reed, improving performance. In addition, the mouthpiece includes a transition from the tone chamber to the central bore of the mouthpiece that minimizes lateral offset and the offset angle of the transition, reducing energy reflection that degrades performance.