The YOB431 is made of top quality aged and seasoned Grenadilla wood for a rich 'professional' sound. This is the same material as used on our Custom models and it has been carefully crafted in a similar manner. It features accurate intonation, a balanced response, and exquisite tone. Truly professional quality at an intermediate model price. The 431 has a semi-automatic octave system and the keys are hand-adjusted by experienced artisans for superb playability.