Audacity is a free, easy-to-use and multilingual audio editor and recorder for Windows, Mac OS X, GNU/Linux and other operating systems. You can use Audacity to:
•Record live audio.
•Convert tapes and records into digital recordings or CDs.
•Edit Ogg Vorbis, MP3, WAV or AIFF sound files.
•Cut, copy, splice or mix sounds together.
•Change the speed or pitch of a recording.
TLA-team: Considering that it is freeware you get quite a lot: features of modern multi-track audio software (including navigation controls, zoom and single track edit, project pane and XY project navigation, non-destructive and destructive effect processing, audio file manipulation (cut, copy, paste)), almost the standard canon of effects ( pitch, speed, tempo change, noise-removal) – additional effects can be self-written with the so-called “Nyquist prompt”. And there is a draw tool that lets you draw on sample-level. Moreover audacity is able to make internal calculations in high quality, for example in 32 bit floating point.