Dan Mulligan is a music educator, barbershopper, arranger, and percussionist from Shorewood, Illinois. He has been involved in barbershop music since 2016, and sings bass with Onset and the Sound of Illinois Chorus. Dan writes arrangements for the contest stage, as well as for show purposes. His arrangements have been sung by groups like Onset, Linc 182, the Sound of Illinois Chorus, and the Midwest Vocal Express. He holds a Bachelor's of Music Education from VanderCook College of Music in Chicago, Illinois. Currently, Dan teaches multiple choirs at William B Orenic Intermediate School and Troy Middle School.

Dan sings bass with his quartet, Onset. The quartet won the Illinois District Quartet Championship in 2022, and is based in the Chicago suburbs. Dan's arrangements are frequently sung by the group at contests and shows.

You can find more information about the quartet at https://www.facebook.com/onsetquartet