Lovers of A Cappella music in 2016 were well served locally by singers who don’t need anything but great voices to entertain. The holiday season afforded two opportunities to hear polished performances by male singers and beat-boxers. The Cincinnati-based “vocal band” No Promises conducted its Christmas tour of six cities in western Ohio, including its second-annual holiday performance at the New Thought Unity Center in East Walnut Hills. Two days later, Straight No Chaser brought its “I’ll Have Another … 20th Anniversary Tour” to downtown’s Aronoff Center. That group, launched at Indiana University in 1996, has built a national following with great performances and a genuine sense of humor. No Promises, nopromisesvocalband.com; Straight No Chaser, sncmusic.com.