While they're mostly known for their disco era songs like Stayin' Alive and Night Fever, for me, I honestly don't think it gets much better than How Deep Is Your Love. It's just such an amazing song on so many levels. The composition of it is something where it really hits a lot of my favorite techniques that I really love about a lot of songs from the 70s. The use of harmonies, the layering, the instrumentation, the chord progressions, and just how emotionally powerful of a song it is. There were a few groups from that time that all had songs that touched on these notes, Earth Wind & Fire's "After The Love Has Gone" comes to mind (also a BIG RECOMMEND if you've never heard it before!).