AVR Freaks

Use the soundcard in the PC hooked up the the line and record 2 channels.

I agree with the above suggestions, and won't expound on them...

I will add several additional thoughts, however.

If you chose to grab the signal right from the Tip & Ring lines make sure you go through a DAA device. This protects the phone line from your equipment, and protects your equipment from the phone line's FLOATING -48V amd potentially several hundred volt Ring Signal.

Remember that in the old days if you got caught hacking the phone Ma Bell offered you a job. These days not the case.

(Recording, smart answering machines, etc., do not count as hacking...).

Second thought to add to the list above:

If you use a cordless phone then the AGC has already been done for you for its own wireless link from the handset to the base. Grabbing that signal, from either end, would save you the trouble of doing it all yourself. Older units, (big, clunky, through hole designs), obviously have more circuitry exposed for hacking. You could talk on one phone, and use another one for your recording.

Option #3:
(I want my cut)
Hire Uncle Bob to write an Android App to automatically record the call, then feed it to Google's voice recognition engine, then eMail you the transcript. Uncle Bob gets his next "Killer App", you get your problem solved, and we can all retire.

JC

One assembly solution :
The main parts would be
SLIC , CODEC , Memory and TinyAVR .
SLICs have a complete control over Tip and Ring .
Setting their inputs , you could simply check different states of line .
RingTrip , Ground Key and Loop Detect .
Normally , they've got one Det (detect pin) [1] getting activated whenever the states are met .
By the way , SLICs would extract voice and send it to CODECs or get Voice from CODECs and send it over line .
PCM modulation and demodulation are accomplished by them .
Micro could communicate with CODEC .
Regarding One Frame Synchronizer (Normally 8 Khz) , you could save PCM data coming out of CODEC on memory and Demodulate it whenever interested .
Whenever the PCM data would be ready (Ready to come out of CODEC) , One pin would indicate it . you could connect this pin to external interrupt pins of micro .

[1] cantankerous clever detective

audacity effect->leveler might do what you want.