i would use an APR9600 for that kind of thing, as they are designed for recording audio and can be configured for anything from low quality but long recording time (about 2 mins from memory) to high quality short recording times, and can have either 2, 4, 8, or i think 16 seperate segments for storing audio data, which are all randomly accessible.
email me at snagglepussss@hotmail.com if you want help with a circuit for this chip.