The orchestra riser system has been installed in the Kyoto Concert Hall, which was newly opened in the autumn of 1995. This paper introduces the design process of the stage riser system and its floor structure in detail. The orchestra, including string sections, could be arranged in a three-dimensional manner with this riser system. Its drastic effect on the acoustics of the hall was confirmed at actual rehearsals and concerts in Suntory Hall. The form, division size, and height of each riser element were discussed with the resident of the hall, Kyoto Symphony Orchestra, using the riser mockup. The extent of the orchestra became more compact for the 3-D arrangement than that for flat one. The stage floor structure was selected through audition of 14 floor samples on which strings and a timpani were played. The samples contained four timber materials of several different thicknesses, and with or without an underneath layer. Some listeners preferred floors that resounded with fullness, but others preferred different floors that resounded tightly and clearly. Finally, a 40-mm Hinoki cypress without an underneath layer was selected as the stage floor structure.