I just came across these amazing videos.. Nyle Steiner has these up on
YouTube... tiny oscilloscope using a cathode ray tube.

as posted on Matrix Synth:

http://matrixsynth.blogspot.com/2006/09/homemade-cathode-ray-tube-oscilloscope.html

Now who wouldn't love to have one of these mounted in their Doepfer

Maybe it's impractical (I don't know electronics) but one can dream, eh