With God's help, the "Anna Regent" application appeared.
In the application you can:
Adjust the volume of each part.
Turn on and off parts individually.
Listen to every part.
Sing your part to any of the parts.
Listen to the singing on the piano.
One, two, three and four parts will be included at the same time.
The parts are recorded separately. When one party is playing, the others cannot be heard.