Windows 10 users will be able to record and play back any phone calls they receive or make with its Phone app. That's what the Windows Store listing for the app shows, which was found as part of this weekend's leaked Windows 10 build 10558 build.
The store listing says:
"Record your phone calls-cellular, Voice over LTE or Wi-Fi-for future use and playback (requires consent from all parties on the line)
As we noted this weekend when the Phone app appeared with this build 10558 leak, it doesn't really do much at the moment, but the call recorder feature in the store listing will likely be added in a future version.
Thanks to @Sachin_990 for the tip!