Features

Current Features

OSS (/dev/dsp) support
Win32 (mmsystem.h) support
Component-based design
Object-oriented internals (written in C)
Plugin-based implementation
Ugly, yet functional user interface
Runs on Linux and Win32 platforms
Links against libaudiofile to provide flexible sample I/O
Able to string together and loop an arbitrary number of sequenced measures
Loads LADSPA plugins.
Multiple Sheets (subroutines)

Plugins currently available

ADSR envelope (for arbitrary control)
Arc-tangent "compression"
Timer/Clock
General-purpose control (UI element)
DC Bias
Delay (with feedback)
Variable Delay (with feedback)
Simple event-processing components
Gain component
File Requester
Envelope Gain
Joyport Control
Midiclock in (not really tested because i have no midi equipment)
ogg_reader plugin
Oscillator (sine, square, sawtooth, triangle)
Audio Output plugins
Pattern Selector
Scope
White Noise Generator (Linux only, for now)
Random-access to Realtime converter
Resampler (simple pitch-shifter)
Sample reversal plugin
Level/Note/Trigger sequencers
Smooth fader
Low-pass resonant filter
Sampled Voice
Simple cross-fade component
A simple WAV recorder plugin to save a session's output

Planned Features

Some of these will make it into forthcoming minor releases. Some will be addressed during the next major release cycle. There's no particular ordering of the list implied, either.

Save/Load/Play "performances"
Prettier, easier-to-use user interface
Full keyboard support
Support for more audio-IO libraries (ALSA, ESD-alikes etc)
More (and better) plugins
More (and better) examples and samples
Improved control-panel
Improved off-line (non-realtime) processing
Proper support for 64-bit machines
Optional full-integer-math internals

And some (semi?) far-off ideas:

MIDI support. (There is some untested midi support which will get better if someone would use it and send feedback to me)
Network-aware plugins, allowing distributed gAlan for really heavy number-crunching work. (Something CORBAish, maybe?)

(distributing gAlan would allow a couple of nifty things: sharing CPU load over many machines; two people collaborating on a piece of music in realtime; etc etc.)

Plugins on the drawing-board

Improved sequencer plugins
Proper "drum kits"
Compressor/Expander/Gate/Limiter
More (and better) filters