Update 3/25: New instructions that are more concise.
Update 3/16: New DLL for CDMA users (now working)!
Special thanks to: XDA in general, monx, indagroove, Calcu, Slypher
If you are a CDMA user, you have one extra step (step 3). GSM users should not do this step (it will mess you up!)
Requirements: Slide To Answer PhoneCanvas for your network type (CDMA S2A for CDMA users, GSM S2A for GSM users).
1) Install the CAB file, "InCallRecording_repacked_monx.cab".
2) Copy everything in the "Copy to Windows" directory into your phone's \Windows directory. Overwrite everything. You will probably need to use Total Commander or similar file manager in order to copy these files.
The files are: ICR_BEEP.wav, ICR_BEEPBEEP.wav, and voAMRNBENC.dll.
CDMA ONLY: 3) Copy wavedev.dll from the "CDMA DLL" folder into your \Windows directory (using Total Commander) Backup wavedev.dll first!
4) Soft reset.
5) Open your new program, "In Call Recorder". Go to options, set Audio Format -> WAV, Store Location -> Card.
6) Start a call. Once the call is connected, hit your right menu softkey and at the very bottom it should show you an option to Start Recording. Call has to be connected (timer must be going) for this not to be greyed out.
7) Files are stored in Storage Card\Recording or Internal Storage\Recording as WAV files. You can also listen to them in Programs > In Call Recorder.
I have it working on: MightyROM 4.8 Diamond, however another user posted and said his is not working...
PREINSTALLED ON:
GrooveROM 4 Diamond
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IF ALL ELSE FAILS: Try someone else's solution
http://forum.ppcgeeks.com/showthread.php?t=58327