Audiality is a highly scalable and portable audio engine and synthesizer. MIDI files are used in combination with scripting and modular synthesis, to minimize file sizes and maximize flexibility. Audiality can be used as a music and sound effects player in multimedia productions, or as a realtime MIDI synthesizer.
The Audio* Music Synthesis Project is music creation software. Currently it features Mojo Synth which is a polyphonic analog modelling synth that has a 64 step sequencer and can also be played from a MIDI keyboard. It attempts to emulate classic analog sounds from Roland M-100, Korg MS-20, and Mini Moog synthesizers.
iabc is a graphical application for editing music. It uses the ABC music notation language to produce high-quality graphical notation or MIDI output. The music notation and the ABC notation can be updated in real-time, making the construction of tunes using the ABC language hassle-free (or at least hassle-resistant).
GENPO (GENeral Purpose Organ) is a program which replicates the essential features of any pipe, theatre, or reed organ. It reads a description of an organ (a .org XML file) and presents a suitable user interface for operating that organ. There are a number of high quality organ "SoundFonts" freely available and the .org file maps the stop sounds to organ manuals and stops. Other facilities such and couplers and presets are available. You may connect one or more MIDI keyboards to GENPO to provide the organ manuals, and you can even assign one to be the 'pedalboard' if so desired.
Open Sound World (OSW) is a scalable, extensible programming environment that allows musicians, sound designers, and researchers to process sound in response to expressive real-time control. It combines a familiar visual patching paradigm with solid programming language features such as a strong type system and hierarchical name spaces. OSW also includes an intuitive model for specifying new components using a graphical interface and high-level C++ expressions, making it easy to develop and share new music and signal processing algorithms.