VCO idea

[9705146x]

I was just sitting in an electronics lecture and had an idea for a VCO. 
Why not have a repeating waveform that has (say) 4 "lines" of which the 
slope and duration can be adjusted, either by a control knob or voltage 
control. Like this :
        |         |
       / \_       |
\     |    \_     |
 \   /       \_   |
  \  |       ^ \_ |
   \/        |   \|
 ^    ^      |     
 |    |      |    ^
Line1 |     Line3 |
      |           |
    Line2        Line4 


So, in other words, you would have a waveform which has a  constantly 
changing waveform. You could modulate the amplitudes and slopes of the 
lines in any way you wanted creating very strange waveforms. How would 
one go about building a circuit that could do this? Could it be done 
using analogue electronics? Has anything like this ever been incorperated 
in a Serge, Buchla, or Moog modulars?

<bUd> Board shitless in another Computer Systems Engineering lecture ;(