Please read the Open Mic post where is says

NOTE: While we used to allow acapella performances to enter, recently there have been far too many entries of singers without any musicians. Open Mic is a community of musicians and for this reason entries without some musical instrument being performed will not be considered a valid entry. NO KARAOKE

There is a Karaoke contest on Steemit too. Karaoke Contest Week 22 Contestants --- by @killerwhale