Is there a bus that is the null equivalent?

Questions
1

I have a synthdef that has multiple bus inputs. Is it customary to have a bus that is designated to not be in use, so, when I create a synth but need only one bus input, the other is set to the not in use bus? Or can the argument be left undefined?

2

This can be quite annoying. I’d prefer if there was some kind dead bus number (perhaps negative values), but there isnt (to my knowledge).

Yes, make a large bus, like 10 channels, and use that as the initial value.

To help with this you could do this…
I’m on mobile, so this probably has some errors.

~default_bus = (\ar_bus : Bus.audio(s, 10), \kr_bus: Bus.control(s, 10));


~opt_bus = {  | rate, name |
   if(rate ==\ar, {
      name.asSymbol.kr( ~default_bus[\ar_bus] )
   }, {
       name.asSymbol.kr( ~default_bus[\kr_bus] )
   })
};

....

x = { 
   var signal = ...;
   Out.ar( ~opt_bus.(\ar, \out), signal ) 
}.play;

x.set(\out, 0);
3

Yeah I was also trying to see if setting as default SynthDef(\test,{ arg bus=Nil ; ... } would work, but Nil basically equates to 0. So now, i’ll create a ~nilbus=Bus.control(), and use that as a default for inputs.