I am learning a pop song that was famous about a decade ago and starts on an F chord for a few bars before going to the following descending chord progression.
F Eb Dm7 Bbm/Db
The second time the progression is the same except it ends on Bb major and then goes into a staple vi ii IV V progression in F major
The song is notated with one flat but up until that point actually appears to use the notes from the F Mixolydianb6 scale which is the 5th mode of the Bb melodic minor scale. I found this song as I was looking for examples of songs using the mixolydian mode and on the wikipedia page this song was listed as an example. After looking at all the notes used in the vocal melody however, in the 1st verse, there is no M6 but only a m6 when the Bbm chord is used. Is it correct to say that this part of the song is actually using the Mixolydian mode or is it true that the b6 means it is actually using the melodic minor scale in this part of the song?