chani — Reads data from the software bus
kchan -- a positive integer that indicates which channel of the software bus to read
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.
The example shows the software bus being used as an asynchronous control signal to select a filter cutoff. It assumes that an external program that has access to the API is feeding the values
        sr = 44100
        kr = 100
        ksmps = 1
        instr   1
           kc   chani     1
           a1   oscil     p4, p5, 100
           a2   lowpass2  a1, kc, 200
                out       a2
        endin