Free+Software

 http://musescore.org/en

//MuseScore// is a free cross platform WYSIWYG music notation program, licenced under GNU GPL. Some highlights:
 * WYSIWYG, notes are entered on a "virtual note sheet"
 * Unlimited number of staves
 * Up to four voices per staff
 * Easy and fast note entry with mouse, keyboard or MIDI
 * Integrated sequencer and __[|FluidSynth]__ software synthesizer
 * Import and export of __[|MusicXML]__ and Standard MIDI Files (SMF)
 * Platform independent code, binaries available for Windows, Mac and Linux
 * Available in __[|20 languages]__
 * GNU GPL licenced

http://audacity.sourceforge.net/

The Free, Cross-Platform Sound Editor
Audacity® is free, open source software for recording and editing sounds. It is available for Mac OS X, Microsoft Windows, GNU/Linux, and other operating systems.