I actually bought this “program” back in 1994, on tape. Didn’t work so well with the wow and flutter of my walkman, but the underlying concept was sound. That was back before anybody knew what you meant when you said “nobody can be told what the matrix is.”
Originally, i am a bass player. Have good enough relative pitch that i can play fretless in tune. But the concept of the perfect pitch course didn’t really sink in until maybe 5 years ago when i picked up (soprano) flute. The overtone series, as a bass player, just wasn’t that important. Root, octave, 5th, octave, 3rd, 5th, third octave. And on a good day, the maj 2nd thrown in on top. Once i burned those into my mind, as its easier for me to hit the flute harmonics when i “hear” them first, i started to hear the relative amounts of different harmonics in different instruments. Yellow vs pink, as trevor wye suggests. Makes it easier to pick out the fundamental. And it really does lead to strange thoughts, as your mind fine-tunes itself to better “hallucinate” and decompress the raw signal your ears are feeding your brain. Not something you can woodshed, though.
But with whistle (and simple flute) the notes aren’t consistent in timbre. You can cheat, as different notes resonate differently. That just takes familiarity with each instrument you have, learning its sonic quirks.
But what i like to do is tune up a guitar to DADGAD, and strum the guitar. Then go play the whistle while staying in tune with the guitar. Use a capo with a non-D whistle. D-G (4th), D-A (5th), D-D (octave). Just get the D stuck in your head, even after the guitar stops vibrating. Like a drone that doesn’t drone. Then get your E, F#, B, C# to sound properly with the D. Then put the capo at the 5th fret and work on your C natural within the G major scale. Until you can internalize the tonic, it isn’t cheating to use an external pitch source. Ratios are musical. And once you burn the ratios of the D major scale into your noggin, everything else is just sped up or slowed down, relatively speaking.
Then again, both relative and absolute pitch just get in the way of letting Le Sacre flow through you. Music becomes as easy as breathing. But not until it becomes complicated enough that you have a Communication Breakdown. I found i “thought” too much when doing the pitch training freeware games. Its when you stop thinking that the magic happens. And if i could have told myself that back in '94, i never would have listened to myself.