Series II of the Fairlight CMI (computer musical instrument) used dual 6809 CPUs running OS-9, and also used one 6809 CPU per voice card. The 6809 was often employed in music synthesizers from other manufacturers such as Oberheim (Xpander, Matrix 6/12/1000), PPG (Wave 2/2.2/2.3, Waveterm A), and Ensoniq (Mirage sampler, SDP-1, ESQ1, SQ80). The latter used the 6809E as their main CPU. The (E) version was used in order to synchronize the microprocessor's clock to the sound chip (Ensoniq 5503 DOC) in those machines; in the ESQ1 and SQ80 the 68B09E was used, requiring a dedicated arbiter logic in order to ensure 1 MHz bus timing when accessing the DOC chip.