Voice Chirp Circuit for Hours of Audio

See my comments as per the pervious thread on the subject

http://cr4.globalspec.com/thread/43057

If you cannot find a voice record chip with enough memory capacity you can connect external memory chips to increase capacity. Check voice record chip datasheets for details as there will likely be an upper limit and some chips wont support external addressed memory.

Additionally you could consider incoding the audio signal at a lower sampling rate resulting in a smaller amount of memory required per second of audio capture (increasing the duration of audio you can record). Again check voice record chip datasheets as I am not sure which ones may allow this feature (possibly as an external switch select or microprocessor register select.

Power is 2 AA nicad batteries. As power dwindles during use, how will this affect my circuit?

If you implement a capacitive switch with a multi-stage latch function out of discrete devices (like transistors, relays, etc) with the outputs controlling individual microprocessor inputs then as the battery voltage drops the capacitive switch will begin to stop working. The microprocessor and voice record chip will reach the minimum operating voltage level and then just stop. Two AA NiCAD batteries will only give you about 2.4V down to 2V when most of the useful stored energy is discharged, so you will need a voltage boost regulator chip to get the necessary voltage to operate the microprocessor, etc.

I need to be able to goto certains chapters of the programmed audio

This is going to be the biggest problem. Depending on how much you know about microprocessor programming you could implement set chapter widths or settable chapter flags and switch between them using a find next flag function (perhaps implemented by one or two additional switches "Next Chapter" and possibly "Previous Chapter").

What you are proposing is a solid-state memory version of the old tape recorder

http://en.wikipedia.org/wiki/Tape_recorder

http://www.solidstatesound.co.uk/

How much do you know about microprocessor programming, design and general electronics as this project is very complex and requires much more of a detailed knowledge regarding microprocessor programming compared to your previous project?

eg- http://www.solidstatesound.co.uk/edirolr-09HR.htm

Additionally try a google search of "solid state audio tape recorder" for more information and existing products on the market (both professional, consumer and basic and cheaper versions or modules you could incorporate into other products).