#Mathematica 319


    {x_, y_}~t~{c_, d_, e_} := c < x < d && e < y;
    z@n_ := EmitSound@Sound[SoundNote[n, .3, 1]]; r = Rectangle; b = Black;
    Dynamic@ClickPane[Graphics[Flatten@{White, EdgeForm@b, r[{0, 0}, {6, 9}], b, 
      Line[{{#, 0}, {#, 9}}] & /@ {2, 4, 6}, r[{.5 + #, 3}, {1.5 + #, 9}] & /@ {1, 3}}],
      z@Which[#~t~{1.5, 2.5, 3}, "C#", #~t~{3.5, 4.5, 3}, "D#", #~t~{0, 2, 0}, "C", 
      #~t~{2, 4, 0}, "D", True, "E"] &]

![keyboard][1]


  [1]: https://i.sstatic.net/3yKT5.png