## 3 Experiments and Discussion
The rows labeled with \"All pieces\" correspond to the results associated with the analysis of all the music pieces considered in the study (from all three collections). Based on the results of the experiments, it is not possible to unequivocally indicate which type of pitch-class representation gives better results. For example, for the set of [PERSON]'s preludes, better key-detection results were obtained using the method based on the multiplicities of occurrences of individual pitch-classes. In some cases, the differences were relatively large, for example, for the method using the signature of fifths (8.4 pp) or the strictly correlational approach with the Krumhansl-Kessler key-profiles (7.3 pp). However, for [PERSON]'s preludes, the opposite was observed in most cases. The exception was the strictly correlational approach based on Krumhansl-Kessler profiles, which gave slightly better results when applying the multiplicities of occurrences of individual pitch-classes. The differences observed with regard to the pitch-class representation using the aggregate \begin{table}
\begin{tabular}{c c c} \hline \hline
**Collection/Album** & **Efficacy for \(R_{\text{M}}\)** & **Efficacy for \(R_{\text{D}}\)** \\ \hline [PERSON]—The Well-Tempered Clavier (Book I) & 86.5\% & 78.1\% \\ [PERSON]—Preludes Op. 28 & 87.5\% & 88.5\% \\ The Beatles—A Hard Day’s Night & 78.8\% & 82.7\% \\ All pieces & 85.2\% & 83.2\% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Overall * efficacies of the key detection obtained using the signature of fifths for different weighted pitch-class representations of analyzed fragments of music, where \(R_{M}\)—the multiplicities of occurrences of individual pitch-classes; \(R_{D}\)—the aggregate durations of individual pitch-classes. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Collection/Album** & **Efficacy for \(R_{\text{M}}\)** & **Efficacy for \(R_{\text{D}}\)** \\ \hline [PERSON]—The Well-Tempered Clavier (Book I) & 81.3\% & 74\% \\ [PERSON]—Preludes Op. 28 & 80.2\% & 79.2\% \\ The Beatles—A Hard Day’s Night & 73.1\% & 75\% \\ All pieces & 79.1\% & 76.2\% \\ \hline \hline \end{tabular}  
* Based on the results obtained for all of the sample selection criteria (i.e., Beginning, End, Beginning_End, and Whole).  
\end{table} 
Table 3: Overall * efficacies of the key detection obtained for different weighted pitch-class representations of analyzed fragments of music using a strictly correlational approach based on Krumhansl-Kessler’s profiles (K-K), where \(R_{M}\)—the multiplicities of occurrences of individual pitch-classes; \(R_{D}\)—the aggregate durations of individual pitch-classes. Figure 11: The key-finding efficacies obtained for the preludes of [PERSON], from The Well-Tempered Clavier collection (Book I); the samples represented using the aggregate durations of individual pitch-classes. Figure 12: The key-finding efficacies obtained for the Preludes Op. 28 by [PERSON]; the samples represented with the aggregate durations of individual pitch-classes. Figure 10: The key-finding efficacies obtained for the songs from the album A Hard Day’s Night by The Beatles; the analyzed samples represented with the multiplicities of occurrences of individual pitch-classes. Figure 9: The key-finding efficacies obtained for Preludes Op. 28 by [PERSON]; the analyzed samples represented with the multiplicities of occurrences of individual pitch-classes. Figures 8-10 show large differences in the key detection efficacies obtained for the given collections of music. The results depend on the selection of the analyzed fragments of pieces, for example, the beginning or the end of the piece. In the case of [PERSON]'s preludes, this can be explained by the fact that many of the compositions, which are written in minor keys, end in the relative major key. Such endings are found in preludes No. 6, 8, 10, 12, 14, 16, 18, 20, 22, and 24.