I was going to suggest notenumber mode 12 but you got there first

Quoting Steven Yi <stevenyi@gmail.com>:

> An array would be a good generic solution.  For one specific to just
> black-key or white key, you might want to write a UDO that checks if a
> note num is a black key.  Something like:
>
> opcode is_black_key, i, i
>    inotenum xin
>    ival = inotenum % 12
>    xout (ival == 1 || ival == 3 || ival == 6 || ival == 8 || ival == 10)
> endop
>
>
>