chano — Send data to the outwards software bus
xval --- value to transmit
kchan -- a positive integer that indicates which channel of the software bus to write
Note that the inward and outward software busses are independent, and are not mixer buses. Also the k-rate and a-rate busses are independent. The last value remains until a new value is written. There is no imposed limit to the number of busses but they use memory so small numbers are to be preferred.