# Evaluating Preprocessing Techniques for Unsupervised Mode Detection in Irish Traditional Music
## 4 Results and Discussion
### PCP Configuration Experiments  
Tables 1 and 2 present the performance of the selected unsupervised algorithms on various PCP representations. Each row corresponds to a specific musical mode (Dorian, major, minor, or Mixolydian), while each column represents a different PCP configuration, as detailed in Section 3. The values in the table indicate the evaluation metric of purity for different classifiers. Furthermore, Tables 3 and 4 show the evaluation of Normalized Mutual Information (NMI) and the Adjusted Rand Index (ARI). The best results are highlighted in bold. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & & **Simple PCP** & **Weighted PCP** & **Binary PCP** \\ \hline \multirow{4}{*}{K-Means} & Dor & 0.8826 (C1) & 0.7737 (C1) & **0.7542 (C2)** \\ \cline{2-5}  & Maj & 0.9744 (C2) & 0.7635 (C3) & **0.9798 (C3)** \\ \cline{2-5}  & Min & 0.6633 (C1) & 0.7758 (C1) & **0.8066 (C4)** \\ \cline{2-5}  & Mix & 0.4600 (C1) & 0.6678 (C1) & **0.6600 (C1)** \\ \hline \multirow{4}{*}{Agglom.} & Dor & 0.6329 (C2) & 0.7062 (C4) & **0.6919 (C1)** \\ \cline{2-5}  & Maj & 0.6246 (C3) & 0.8241 (C3) & **0.9152 (C3)** \\ \cline{2-5}  & Min & 0.7597 (C2) & 0.6710 (C4) & **0.7280 (C4)** \\ \cline{2-5}  & Mix & 0.5189 (C4) & 0.4798 (C3) & **0.9033 (C2)** \\ \hline \multirow{4}{*}{DBSCAN} & Dor & 0.9999 (C1) & 0.99 (C1) & 1.0 (C1) \\ \cline{2-5}  & Maj & 0.9992 (C1) & 0.99 (C1) & 0.9997 (C1) \\ \cline{2-5}  & Min & 0.9997 (C1) & 0.99 (C1) & 1.0 (C1) \\ \cline{2-5}  & Mix & 1.0 (C1) & 0.99 (C1) & 0.9956 (C1) \\ \hline \multirow{4}{*}{Mean Shift} & Dor & 0.9258 (C1) & 0.9136 (C1) & 0.9948 (C1) \\ \cline{2-5}  & Maj & 0.9244 (C1) & 0.8813 (C1) & 0.9992 (C1) \\ \cline{2-5}  & Min & 0.8785 (C1) & 0.9018 (C1) & 0.9664 (C1) \\ \cline{2-5}  & Mix & 0.9350 (C1) & 0.9160 (C1) & 0.9991 (C1) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Performance results of different classifiers using different types of PCP: Simple (Simple), Weighted (Weight), and Binary (Binary). The number in parentheses indicates the dominant cluster for each mode. In the tables of results, each cell reports the purity score along with the dominant cluster number for each mode, providing insight into how well the algorithm distinguishes between musical modes. Furthermore, NMI and ARI scores offer a broader evaluation of clustering performance beyond purity alone. Although high purity indicates that individual clusters are dominated by a single mode, NMI and ARI help to assess whether the modes are meaningfully differentiated rather than arbitrarily grouped. Cases where multiple modes are assigned to the same cluster despite high purity suggest that the algorithm has failed to achieve proper separation. Thus, a comprehensive evaluation must consider all three metrics to ensure that the four musical modes are not only internally consistent within clusters but also well differentiated from each other. \begin{table}
\begin{tabular}{c c c c c} \hline  & & **Simple PCP** & **Weighted PCP** & **Binary PCP** \\ \hline \multirow{4}{*}{SOM} & Dor & 1.0 (C2) & 1.0 (C4) & 0.9707 (C1) \\ \cline{2-5}  & Maj & 1.0 (C2) & 1.0 (C4) & 0.9943 (C4) \\ \cline{2-5}  & Min & 1.0 (C2) & 1.0 (C4) & 0.9983 (C1) \\ \cline{2-5}  & Mix & 1.0 (C2) & 1.0 (C4) & 0.8259 (C4) \\ \hline \end{tabular}
\end{table} 
Table 1: _Cont._