The number of tabs shown for each progression under “Popular Chord Progressions” is often different from the number of songs that “Search by Chords” finds for that progression. Why is this?
The biggest discrepancy that I’ve found (I haven’t checked them all) is for the cadential 64 progression IV - ii - I64 - V - I, where 155 tabs are listed but “Search by Chords” doesn’t find a single song! It finds 141 songs for I64 - V, so it seems “Popular Chord Progressions” is listing all the tabs with I64 - V instead of just those with the whole progression. After taking this apparent mistake into account, we’re still left with a discrepancy of 155 vs. 141. This is similar to the discrepancies for most of the other progressions listed, but where does it come from?