With TouchOSC[1], you can hit on your phone and play a variety of instruments on your computer.
If the TouchOSC is a gun, the layout is a bullet. Now I have developed a new layout.
In TouchOSCEditor (Linux): 
In TouchOSC (Android): 
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Footnotes
[1] h e x l e r . n e t | TouchOSC: https://hexler.net/software/touchosc