Joseph, just because you remember something doesn’t mean everyone else does. Your community prepared for selichos with a mussar drosho. Other communities prepared by sitting together at a melave malka, singing, bonding, being inspired to serve Hashem with simcha, and then at midnight turning to Him to beg forgiveness. Then after selichos, dancing and singing with joy, confident that He will respond.
During the selichos themselves the joy is of a different sort, וגילו ברעדה, but singing has always been traditional, in every community. What else is chazonus? On Yom Kippur itself, who does not sing אשמנו and ועל כולם?
So the only innovation, if it is one, is the use of instruments, since it’s a weekday. And what is wrong with that? The issur is only on organs, not guitars or violins or drums.