This is from a stage play, Porgy and Bess, with all African Americans in the roles. This song has been covered by everyone! It was from the 20s or 30s! Glad you liked it!
Bobby Hatfield and Bill Medley are not Brothers but maybe they're sole Brothers but they're very good friends so they were I say were because Bobby Hatfield passed away in 2007 in his early or middle of 60s. Way too young Bill Medley is still alive and still singing. I have heard summer time different times also like you did but not like Bobby Hadfield he's the best.🤩🤩
I think Bill's solo that followed was "Old Man River" which was wonderful and it's online. The Righteous Brothers were more noted for their R&B so there are more black & white Shindig show performances that will show how they could let it rip like this (I Need Your Loving Everyday is a good start). You will definitely get to see their wilder and funnier sides (Justine & Ko Ko Joe). They truly were great all around entertainers.
Bobby put his own spin on this song, Ella Fitzgerald did this song as well. Bobby rocks on this song, it does show his range of octaves. Take a listen to ebb time, what a beautiful version. Actually unchained melody was his very best. What a blessed man, with a god given gift; his voice. He was dearly blessed, and missed dearly.