Conversation so far:
What did Four Tops do in the later years?
From the late 1980s, the Four Tops focused on touring and live performances.
Where did Four Tops tour in the late 1980s?
Did Four Tops perform any singles on the TV specials during their later years?
Four Tops was featured in several television specials during this time, including Motown 45, and several by PBS
What other events did Four Tops part in besides TV specials?
The Four Tops had a 50th-anniversary concert dedicated to the group (available on DVD).

Question: Why was it bittersweet?
Self-contained rewrite: Why was the 50th-anniversary concert dedicated to the group bittersweet?