Flatline rectifier network q - is there an 'ideal' Fv for the diodes?

[midwayfair]

I've built a few Flatlines (on Madbean's "Afterlife" board and breadboard), using slightly different parts each time. This time around, I skipped the 1N270s because I had some 1N60Ps around, and I thought to myself: Why bother with a 75c diode when I can use these 2c ones that have the same Fv? It sound pretty much the same. I know that 1N34a works, too, even though their Fv is quite a bit higher.

So my question: Is there any change to the sound that come about by using different Fv values here, or is the only important thing to use something with Fv < ~.4v & are these just stop lights for the electrons?

[R O Tiree]

The diodes are there to rectify the signal going to the LED and the 100µF cap.  If the Vf gets too high in those diodes, then the LED won't switch on until a higher signal strength is achieved. This means that the LDR will be at max resistance (therefore max gain in the first opamp) earlier in the decay phase of the signal.

Unless I'm totally wrong?