www.kvraudio.com/news/vopm_for_os_x_released_4792
VOPM for OS X released
10th February 2006
VOPM, the open source, freeware, emulation of the Yamaha YM2151 (OPM) 4 operator FM sound chip, has been ported to Mac OS X VSTi by Mr BouKiCHi.
KVR Audio, Inc.
www.kvraudio.com