Pass a triangle wave through the lower half of a signal processor and give it a 
five volt offset. Then, put it through the rectifier and listen to the result. It 
should still sound like a normal triangle wave.

Now, slowly turn the signal processor offset from five to zero. As the offset is 
lowered the bottom points of the triangle wave will be rectified, adding some 
interesting harmonics. When the offset reaches zero you will have a simple 
triangle wave again but it will be one octave higher. 

You now have a new range of waveforms to explore. Experiment with various 
offsets. Checkout the new harmonics by sweeping your filter and listening to the 
band pass output.

For dynamic voltage-controlled waveforms use a mixer to combine a triangle wave 
with an envelope and put the result through the rectifier.

When you have finished experimenting with triangles, start over and try 
everything again with a sawtooth wave. A rectified sawtooth wave produces a 
triangle wave with the same frequency. You should also try sine waves. Pulse 
waves, however, do not do anything interesting when rectified.