WaveTracker
An advanced chiptune music software, WaveTracker lets the user draw in up to 100 custom sound waves, and use them in up to 100 custom instrument presets. It also features 24 sound channels, a noise generator for drums, a multitude of effects, importing and editing audio samples, and a built-in song visualizer.
There are lots of cool digital signal processing effects under the hood, such as frequency modulation between two waves, lowpass filters and global downsampling, and even a custom "smart" resampling mode that reacts to the drawn wave to preserve crispness for sharper waves but not be too harsh for smoother waves.
> wavetracker.org