I have a few tips for anyone building the Pocket Tutor:
1. The power supply needs a decoupling capacitor across the battery. You should solder an additional 10uF cap across the pins of the battery jack J1.
2. The audio and key jacks are recessed by about a millimeter. Normally this isn't a problem, but one my plugs fails to make good contact. So, when soldering these jacks, please situate them as close as possible to the board edge. The extra-large soldering pads give you some leeway.
I updated the builder's guide to reflect these two changes.