CyanogenMod adds call recording on nightlies; feature is not available automatically
The CyanogenMod team says the feature is available starting with the more recent nightlies but it will not be activated on ROM downloads because there are lots and lots of laws regarding call recording all over de world. If anyone wants to use it they will have to build from source and enable it via system property persist.call_recording.enabled. It’s obviously difficult to do that if you’re not well versed in Android ROMs, therefore you can try the Xposed module which enables the feature on CM 11 builds fron 8.14 or later.
The audio quality seems to be ok and most of those who tried it already, are hoping that the feature gets more attention from developers so that it will be worked upon in detail. Some CyanogenMod partners may choose to allow call recording by default as well in the near future.