About the key signature, nobbler. The keys of A Minor also have no sharps or flats in the signature. There are various other scales, lydian, mixolydian, etc, That is why I added the extra condition about listening to where it is rooted.

You are right about chords. They will pin down the scale. Let me be more precise (another way of saying "change the rules in mid-stream :) When I used the word "tune". I meant just one stave of music with the melody written out.

The above may seem like a funny restriction, but that is where the question arose. I looked at a few scores in my Dover anthology of slave songs, and saw that they used more than five notes. The "scores" consisted of just melody lines and words. I concluded that the tunes were not pentatonic by counting notes used.

Later I thought that even our familiar (Major, minor) scales used more than seven notes. In a well-tempered situation, our notation allows us to write twelve, but in a non-well-tempered situation we can write any number (C, C# C##, etc.) That led me to believe that I was more than a bit naive thinking I could determine a pentatonic scale by just counting notes.

I think I can learn to recognize the verious pentatonic scales when I hear them played. But that is not the same as recognizing if tunes are played in these scales. My question was to see if there was a way to look at a tune in written notation, and hear some or part of it to discover if it is in a pentatonic scale.

Murray