In my experience, the band level is very important because they affect the concert results. So lower chance of unit dying and higher chance of unit promoting. My level 4 rock band with Album Cover Art promotion has 4% to lose on wonders (level 6) and gets 6 stars quite often. What I expect is the game adds a random number to rock band level, and compare that to BaseProbability values to determine concert results. (the XML says <!--BaseProbability needs to be within 3 and 18. Must be specified from highest BaseProbability to lowest-->) 3~18 sounds like sum of 3 dices. You know what? The chance to get 10 or lower number with 3d6 is 50%. And chance to get 9 or lower is 37.5%. 8... 25.93% 7... 16.2% 6... 9.26% 5... 4.63% I think these numbers look familiar.