What is it about using a III chord or a iv chord in a major progression that sounds so goooooood????... is that #5/b6 (in C you'd have the G# from the Emaj and the Ab from the Fmin) like a magic note or something?? So much emotion built in there if you use it in just the right way.
yes it is a very strong note and it is a secret weapon that has been passed down through the ages. just when you think it's forgotten, someone comes back around who knows how to use it and they rake in the cash handily