Purpose of Q1 & 3 in Small Clone Chorus

[Scruffie]

I've been digging in to the small clone recently and i'm wondering, what does Q1 actually do...

I see in the original factory schematic, when the circuit changed had the SAD1024 it used a 2N5088 to 9V and had 3 diodes facing the opposite direction to the MN3007 Version which has a 2N5087 to Ground and one diode the other way. I assume it's something to do with BBD polarity but I can't work it out.

For that matter, why is there a transistor between the power & BBD & Clock, just voltage filtering of some kind?

Factory Schematic - http://sites.google.com/site/electroconducive/EHXSmallCloneSAD1024AMN3007-FactoryE.pdf