You will hear a melody played in a high register with an accompanyment in a low register. Which of the three presentations sound best in tune?
Stretched and compressed scales
This demonstration, for which we are indebted to E.Terhardt, illustrates that
to many listeners an over-stretched intonation, such as case (b) is acceptable, whereas compressed intonation (a) is not. Terhardt has found that about 40% of a large audience will judge intonation (b) superior to the other two. The program is as follows:
a) intonation compressed by a semitone (bass in C, melody in B);
b) intonation stretched by a semi tone (bass in C, melody in C#);
c) intonation "mathematically correct" (bass and melody in C).