Hmm...  Now I'm confused.  The manual says that the ValueKeys are deltas, 
not actual key values.   But if that's the case, the tone-arm action shouldn't work.

The first -12 would raise it; the next -12 would raise it again but hit the limit, so
it would accidentally look the same as a non-delta entry of -12.  But the 0 on the 
last key should leave the arm up if the values were deltas.  

(It would have to be +12 to lower the arm if we were doing deltas.)

In fact the arm does return down to 0, as you'd expect from a non-delta entry.  

So which is it?  Deltas or plain values?

My python page
My ShareCG freebies