I've learned that the changes are actually relatively forgiving. Many of the fake book changes are different from the harmonies that were used when the tunes were show and popular tunes.
Also, even if you're a rhythm player, tunes are a lot easier to memorize if you learn melodies. And that helps in two ways. The first is just having a better grasp of the tune, and the second is that if you're unsure of the changes, you can improvise directly from the melody.
Granted, as a bass player I can get away with not knowing all of those 7ths, 9ths, etc. "I solemnly swear to play the root, the whole root, and nothing but the root, so help me Dusty Hill."
Also, even if you're a rhythm player, tunes are a lot easier to memorize if you learn melodies. And that helps in two ways. The first is just having a better grasp of the tune, and the second is that if you're unsure of the changes, you can improvise directly from the melody.
Granted, as a bass player I can get away with not knowing all of those 7ths, 9ths, etc. "I solemnly swear to play the root, the whole root, and nothing but the root, so help me Dusty Hill."