SPP Sound Phone Pranks audio

With Sound Phone Pranks (SPP) you can play audio pranks.
You can record your voice and play it back at different speeds
(faster or slower). Included are also four libraries with sounds
(human,movies, animals, effects). From version 1.2 it is possible to create a personal library of sounds as well.
In addition, you can also record phone calls.

If you want to use this app during a phone call,
your microphone should be able to get the sound from the loudspeaker.
Otherwise, you should use a second phone to make the calls.
This is due to a limitation with the Android system.
Another thing you can do is recording your phone calls.
Any suggestions to make it better are welcome.