Problem Statement

Load at least two prerecorded sounds, and demonstrate as many of these features as you can: Describe: [Note: If it seems to be a good idea, this task may be revised to specify a particular timeline rather than just 'demonstrate these features'.] Where applicable, please categorize examples primarily by the audio facility used (library/API/program/platform) rather than the language if the language is incidental (e.g. "Mac OS X CoreAudio" or "mplayer" rather than "C" or "bash").

Let's start with the solution:

import osproc

let args = ["-m", "-v", "0.75", "a.wav", "-v", "0.25", "b.wav",
            "-d",
            "trim", "4", "6",
            "repeat", "5"]
echo execProcess("sox", args = args, options = {poStdErrToStdOut, poUsePath})