Pulseaudio is a modern linux audio subsystem. It is backed by Ubuntu, and offers an intermediate abstraction between audio devices and their legacy drivers, and a wide range of applications.
There are capable GUI interfaces to Pulseaudio, allowing application streams to be manipulated with a high degree of precision. However, the scripting capabiliites and command line tools are not yet fully developed.
This repository provides some higher level functionality for taking control of your audio on a per-app basis from the command line.