Neighbor Walking Dog And Singing Xmas Carols

I set up my recorder outside on christmas eve in 2016 and unwittingly captured the sound of this anonymous and apparently oblivious neighbor walking his dog and singing "it's the most wonderful time of the year" down my street. Pretty charming!. I've noticed recently how my zoom h4 has this nasty looping hum buried beneath the already disappointingly stubborn background noise whenever i do field recordings. Can somebody point me to a solution?.