Audacity is a cross-platform multitrack audio editor. It allows you to record sounds directly or to import Ogg, WAV, AIFF, AU, IRCAM, or MP3 files. It features a few simple effects, all of the editing features you should need, and unlimited undo. The audio I/O uses PortAudio, which fully supports OSS, Mac OS X CoreAudio, and Windows WMME, and can be compiled with support for ALSA and Jack.
CLAM is a multiplatform software framework for research and application development for the Audio and Music domains. It offers a conceptual model for building systems as well as tools for the analysis, synthesis, and transformation of audio signals using high level representation (notes, spectral peaks, etc.). It also provides multiplatform system abstraction and tools for audio and MIDI file handling, device handling, GUI and XML support, and more. It has proper Linux audio architecture integration (Ladspa, Alsa, OSC, Jack, VST, etc.) and rapid graphical prototyping both for the processing core and the user interface (Qt designer integration).
DansTuner is a program to tell you if you are playing a pitch in tune. Major features include automatic discovery of which note you are trying to play (good for trumpet, singer, etc.), the ability to play a guide tone at a configurable volume, a graphical moving "needle" with a red/green display and detail about how flat or sharp you are, and an easily configurable background noise threshold.
Embedded Profiler is low-overhead C++ profiler based on automatic instrumentation of functions done by the compiler (GCC, MinGW, or MSVC). Profiling can be done either automatically or manually. Automatic profiling generates a complete call tree and needs no modification of code. Manual profiling requires using the EProfiler API to specify the parts of code to be profiled. The resulting log can be opened in Performance Analyzer, a GUI application with several views designed for comfortable log analysis.
FMS is a tool to create all kinds of sounds from scratch. You can play any sound (sine, triangular, vowels, etc.) with any property settings (frequency, volume, balance, sweep, etc.) and modulations thereof. It also features tools to save sounds, play .MUS music, graphically display sounds, and make real noise.
Frocor, the F Resonating Objects Correlator, is a sound- graphics installation. It is based on some parallels between sounds and geometric objects, such as volume and size, frequency and color, etc. Changes of properties of a Frocor object will result in changes of both the graphics and the sound output.
HASAS (HydroAcoustic Signal Analysis System) is a modular system for passive sonar signal analysis. It can be used for biological research or surveillance, for example. The soundcard is used as input device, and it currently includes all the very basic functionality; beamformed audio, direction finding, level histogram, LOFAR/DEMON (narrowband spectrogram), wideband spectrogram, and raw audio.