• What is the Whistler?

The Whistler (© Patxiku ) is the animation showing the fingerings on Playintune.net

• Why does the Whistler plays the tunes higher or lower than on the original midi file?
  

There are 2 reasons:

First, the music intrument used in the original midi file might be able to play a range of notes larger than the range of a D tin whistle. The Whistler automatically change the global height of the tune to let the notes fit on the tin whistle.

Second, the whistler optimizes the global height of the tune to be able to play it as easy as possible on a D tin Whistle.

• Why are sometimes the original midi file's tracks hidden?

A midi file is most of the time divided into several instrument, one instrument per track. A tin whistle can not play correctly a track written for a guitar for instance, since the guitar can play several notes at once (polyphonic instrument) whereas the whistle can't (monophonic instrument).

Thus the Whistler hides polyphonics tracks.