On some whistles, I can get 3, sometimes 4 notes in the third octave. This involves using special fingering, which is usually slightly different for each whistle. This also involves carefully controlling the overblowing. On some instruments, I get better control by keeping the top three holes closed, and using the overblow 'tabor pipe' technique. It must be remembered that some of the produced notes, if you look at the musical theory, are not 'on pitch' for the tempered scale, but can be 'blown in' to be close enough. Also, one is using the 'harmonic series' of the overblows, (cornet players know what I mean) so some tones are microtonally 'off key' and one must skip some of them intentionally.