Because Call Recorder is using a work around the process to record a call is a little cumbersome and works best if you make a call in speakerphone mode (so that the app can "hear" the other end of the call). Here are the necessary steps to record a call, as described by the developer:
1. Make a phone call or answer the call.
2. Tell the other party that "You are going to record the call."
3. TURN ON the speaker for best quality.
3. Tap the Windows key. It returns to the start menu.
4. Open the "Call Recorder".
5. Tap the microphone icon to start recording. (Icon turns into red to indicate it is recording)
6. Once the call is over, Tap the microphone icon again.
Switching to speakerphone mode does mean that call recording is really only going to work in a quiet environment and using an indirect recording method also has an inevitable impact on audio quality. However, it does work, and should be more than sufficient as an aide-mémoire.
Once a call has been recorded, you can play it back via the playback section of the app. You can also, optionally, add a name and number to note who you were talking to, and mark a recording with a star to indicate it as important. Recorded call can also be uploaded to SkyDrive from where the audio file can be downloaded to other devices or shared with other people.
Do note that you must inform the other party before recording the call and that some countries have laws and regulations around what type of calls can be recorded.
Call Recorder is available in two versions. A free, ad-supported, version (Call Recorder) and a paid for version (Call Recorder Pro), which costs £1.49 / $1.99 / €1.99. The developer notes that this "is just the first version of the app" and that in future release there will be "improved quality for non-speakerphone calls".
While Call Recorder will install to a 256MB device (e.g. Lumia 610) in our tests call recording failed to work correctly. There were no such problems in a 3 minutes test call on the Lumia 900.