Abstract: An asynchronous interface between a data input system (computer) and the keyboard multiplexer of an electronic musical instrument (digital organ) includes a pair of RAMs. The interface synthesizes the multiplexed keyboard data stream of the digital organ by swapping read and write operations between the two RAMs. Predetermined key data (WRITE DATA) provided by the computer is written into one RAM during a WRITE interval while key data (READ DATA) previously written into the other RAM is sequentially read out of the latter RAM. The WRITE DATA designates those keys on the organ keyboard which are to be simulated as being active. The read and write operations are alternately applied to each RAM. If the READ DATA matches the key code assigned to a key on the keyboard, the appropriate note is sounded by the organ. The two RAMs can actually be two segregated portions of a single memory.