[retailer]

I did give the tremelo some thought, the neon/ldr simply shunts the signal to ground, simple.

The bias voltage tremelo at first glance looks to compromise the bias voltage however if you look at the circuit it is in essence a LF oscillator, capacitor coupled to the output valve grids - the guitar signal does exactly the same thing, I may be very wrong here but I can't see any difference apart from the frequency of the two signals, the guitar signal and tremelo oscillator both vary the output valve grid voltage. The upside to the neon/ldr idea is that only the vibrato/reverb channel is affected - like you say if the amp is shared between two band members then there is a problem with the bias voltage method. There were quite a few Fender amps that used the bias voltage tremelo, perhaps this is why Fender moved away from this idea, I have heard it was quite common in the 60's for an amp to be shared between two band members.