E.L.O. - Electric Light Orchestra

So, I'm going through my third, or maybe fourth, ELO music evolution and need your suggestions. I started listening to this group when I was in High School during the 1970s. Currently, I own a couple of their albums. I had several more but I shared them with friends over time and never saw them again. Anyway, what are your recommendations for ELO albums to compliment "On the Third Day" and "Eldorado". Also, anyone who can tell me the name of the instrumental song that is their masterpiece would be appreciated. I remember listening to it at midnight on a local radio station in Virgina. It started off with a crack of thunder and then went into this incredible orchestrated masterpiece that still resonates in my mind to this day. The song was used to announce the beginning of a new day and it was glorious! I haven't been able to find it. Thanks for your thoughts and suggestions.