Quick question... In the program, what's the criteria for it considering something to be a cluster? (And I wonder if the wording in the program should be called "cluster" instead of "comb" but that's not important really.)

It seems to consider any group of songs that is more than two to be a cluster (which is reasonable), but what's the distance-between-songs criteria? It seems like you've chosen a reasonable criteria for this (it seems like I'd perceive the songs to be too close together based on the boxes you've drawn), I'm just wondering what that criteria is.