This is french horn (Single in F).
I made the application assuming that the app play with Surface Pro.
*I don’t recommend playing with iPhone due to playback sound delay in iOS.
movie (from Twitter)
https://twitter.com/KodamaJn/status/1112756796035207168
[control]
This app have 3 valves (same as real horn fingering) for left hand and some buttons that act as a lip buzzing for right hand.
The sound keeps while any button of right hand is pressed. On the other hand, the left hand uses only change the tone.
Please see below about the structure of the french horn:
https://www.yamaha.com/en/musical_instrument_guide/horn/
[material]
I use the free french horn sound file obtained from the website below (University of Iowa Electronic Music Studios).
http://theremin.music.uiowa.edu/MIS-Pitches-2012/MISHorn2012.html
Play fun!!