pebsaq is an interactive synthesizer with support for only sine, triangle and square waves.
Just run this (requires that you have python-setuptools installed):
sudo easy_install pebsaq
Get the newest version of pebsaq at http://metanohi.name/projects/pebsaq/ or at http://pypi.python.org/pypi/pebsaq
Extract the downloaded file and run this in a terminal:
python setup.py install
Running pebsaq with no arguments will start the utility in interactive mode. In interactive mode you can interactively change the frequency and the strengths of the waves. A nice wave will also be drawn to the screen.
Running pebsaq --help will show a list of available command-line options. These options can also be specified in config files. Config files use a property = value syntax (e.g. frequency = 367 or square strength = 2) separated by newlines.
Press 3 to decrease the frequency by 10Hz. Press 6 to increase the frequency by 10Hz. Press down arrow key to decrease the amplitude by 0.1. Press down arrow key to increase the amplitude by 0.1. Press 1 to decrease the sine strength by 1. Press 2 to increase the sine strength by 1. Press 4 to decrease the square strength by 1. Press 5 to increase the square strength by 1. Press 7 to decrease the triangle strength by 1. Press 8 to increase the triangle strength by 1. Press 0 to mute pebsaq. Press ESC to exit pebsaq.