This patch is similar to the abgate~ abstraction for "Routing a signal to one of two destinations" with a fade from one to the other. However, instead of routing one input signal to one of two outlets, this abstraction permits you to choose one of two input signals to send out its lone outlet.
This patch is quite similar to the onoff~ abstraction for "Turning a signal on or off" with a fade-in or fade-out. Instead of just turning the signal on or off, though, this abstraction routes a signal to one of two outlets (with a fade from one to the other), which you can think of as destination A or destination B, based on whether the number in the right inlet is zero or non-zero.
To turn an audio signal on or off instantly, Max provides the gate~ object. However, if you use gate~ to switch a signal on or off while MSP is on, you're likely to cause an unwanted click due to the sudden discontinuity in signal amplitude.
This patch provides a virtual emulator of the popular Behringer BCF2000 hardware MIDI controller.
Even if you don't have a BCF2000, this patch allows you to replicate it onscreen. The patch allows you to control other MIDI devices just as if you did have the hardware controller. Use the umenu to select the port to which you want to transmit, then use the emulator patch to send MIDI control messages.