A free multi-track audio editor and recorder
Audacity is a free, easy-to-use, multi-track audio editor and recorder for Windows, Mac OS X, GNU/Linux and other operating systems. The interface is translated into many languages. The version currently hosted here is 2.1.0 (March 2015). More recent versions than this are available from http://www.audacityteam.org/download/ . Audacity is free software, developed by a group of volunteers and distributed under the GNU General Public License (GPL). Programs like Audacity are also called open source software, because their source code is available for anyone to study or use. There are thousands of other free and open source programs, including the Firefox web browser, the LibreOffice or Apache OpenOffice office suites and entire Linux-based operating systems such as Ubuntu
Nicole Studio music editor!
Nicole Studio is a powerful tracker and synthesizer for writing songs of all genres, it is skin based, cross-platform and written in GTK. Nicole Studio aims to be a open source alternative to popular programs like FL Studio, Cubase, Logic and so on... Linux have some music editors now! Such as: Audacity, Ardour, Traverso, QTractor, Linux Multimedia Studio (LMMS). So Nicole Studio is not under development now!
A cross platform audio inteface
CIOS Audio Core is the infrastructure and subsystem in Collective Intelligence Operation System. It is a cross platforms audio abstract interface, supports including Mac OS X, Linux, Android, iPhone OS and Windows 7.
ibroadcast is a open source internet radio automation system that makes it easy and cheap to make internet radio. It supports ShoutCAST, so no special servers anymore :)