Historically, many attempts to analyze melodies or parts of compositions mathematically or with computers have concentrated only on excerpts or incipits. Scholars believed that these excerpts or incipits are sufficient for representing entire pieces of music. However, the authors usually did not reflect on the possible effects that the length of the musical excerpts has on the analytical results; they did not question the validity of the analytical results. This paper summarizes the use of incipits and excerpts in the history of mathematical and computer-assisted music analysis. Then, using the methodology of falsification, analytical results will show the differences of statistical and information-theoretical results, when different incipit lengths are being used to analyze music. The data provided in this study clearly show that there is no statistical basis for the assumption that incipits have a sufficient size for discriminatory tasks or style characterizations. This study is based on analyses of divertimentos for three bassett horns by Wolfgang Amadeus Mozart (1756-1791).