They did not use data from guitar tabs: >Guitar tab websites have tons of information about the chord progressions that songs use, but the quality is not very

They did not use data from guitar tabs: >Guitar tab websites have tons of information about the chord progressions that songs use, but the quality is not very high. >So, over the past 2 years we’ve been slowly and painstakingly building up a database of songs taken mainly from the billboard 100 and analyzing them 1 at a time.