I have heard of some pretty creative solutions, though.
A family I know volunteered to sing in their ward. They had to do something very simple, but what they came up with was quite successful.
Some wards do InstaChoirs where they ask anyone who wants to join in to just come up and sing a hymn from the hymnal.
Then I heard of a Ward that had all of the men just stand up in their places and sing "Ye Elders of Israel."
The Primary children sometimes get asked to try out one of the songs they are preparing for their Sacrament Meeting Presentation later in the year.
Sometimes, one of the youth is available to play a piano or other instrumental solo.
I am always glad when Fall comes around again and people are more willing to prepare Special Musical numbers for Church. I especially love having the choir sing. Only a few more weeks....
In the meantime, here are a few 2-Part Mixed Hymn Arrangements that have been used successfully for a family or small group or even a duet.
"Abide with Me 'tis Eventide," "Come Follow Me," "Count Your Blessings," and "Israel, Israel God Is Calling."