ABSTRACT We present sndtools, a set of cross platform, open-source tools for simultaneously displaying related audio and vi- sual information in real-time. The distribution includes tools to extract spectral information, perform linear pre- dictive coding analysis and resynthesis, manipulate pitch and time using a phase vocoder, and map text to Morse code. Each tool has closely related audio and visual (graph- ical or text) components and can be used for instructive purposes or experimentation with sound. We show that hardware-accelerated graphics tools such as OpenGL can be used to enable real-time 3D visualization of DSP algo- rithms.