Newbie cannot get new code to compile

Questions
5

  1. ~ in ~mul
    The tilde symbol, ~, followed by a word beginning with a lower character, is used to indicate environment variables. Environment variables act like global variables in the environment in which they are defined:
    Environment | SuperCollider 3.12.2 Help
    Except for large or specific projects, I don’t think there is usually a need to define and switch between multiple environments.

    There are three types of variables in sclang:

    • Interpreter variables
      • Global scope variables, which can be used by assigning a value to the variable:
      • A single lowercase letter from a to z.
      • s is assigned Server.local by default, and users should not reassign it with a different value, as s with the default value is used in the help documents and by many users.
      (
a = 1;
b = 2;
a + b
)
    • Local variables
      • Local scope variables, which should be defined with the keyword var
      • A word starting with a lowercase character.
      (
a = 0;
{
    var a, b;
    a = 3;
    b = 5;
    a + b
}.().postln;
a // This a is outside the code block above, so its value is not 3, but 0.
)
    • Environmental variables:
      • can be used by assigning a value
      • See above for details.
      (
~freq1 = 440;
~freq2 = 441;
~freq2 - ~freq1
)

  2. ! is a ‘syntactic sugar’ (a syntactic shortcut) of dup.
    The following examples are all the same:

    [1, 1, 1]
1!3
1.dup(3)

  3. \ in \amplitudes.kr(...) and \mul.kr(...)
    Please read the thread below:
    NamedControl: a better way to write SynthDef arguments

The following PDF would be very helpful for you (it is really gentle):