Okay so I was looking over the sheet music that I have of all the Wicked songs, and I just noticed something that I've never seen before.

For most of the show, whenever Elphaba and Glinda sing together, Glinda sings the melody/the soprano part while Elphaba sings the harmony/the alto part. However, there are two occasions where this isn't the case.

During "Defying Gravity" when they sing about being a team and defying gravity together and during "For Good".

During those parts, Glinda sings the harmony while Elphaba takes the melody. Those are the only parts in the musical where Glinda doesn't take over the song with her beautiful soprano voice. Instead of singing the melody and letting everyone else back her up like she does at other parts of the show, she lets Elphaba take the lead while she supports her.

I just love their friendship so much oh my stars