Two members travel from Rotorua each week to take part and three travel from Tauranga.
Some members have been with the chorus since it started more than 20 years ago.
Director Jill Rodgers says A cappella is becoming more popular, especially in high schools.
She says Mighty River Harmony enjoy the fellowship of bringing their voices together.
Jill says with the tour they hope to show high schools and the communities how they can enjoy barbershop and the support network it has around the country.
"I love when the audience gets a bit excited about the sound and you see their eyes light up.
"The surprise people have when they hear the sound we make with no instruments - people are quite amazed about that."
Jill encourages people to come along so they can try something new.
"People might not know what Barbershop is and I think it's the best kept secret in singing in New Zealand."
She says a lot of the members of the chorus have helped to put these workshops and concerts together.
The chorus were Silver Medallists in the chorus section of the New Zealand National Barbershop Competitions last year, and will head to Sydney for the Pan Pacific Competitions next month to defend their title.
As part of their preparation for the Sydney competitions, Mighty River Harmony are doing their August tour to spread knowledge of Barbershop and the enjoyment of the music in Rotorua, Napier and Taupo.
The workshop will include aspects such as teaching good vocal technique, learning about diaphragmatic breathing, and the A cappella style of singing and techniques used to make up for no instrumental help.
It will be all about participation with lots of practical application and participants will learn at least one song and perform with the Mighty River Harmony chorus during the concert that evening.
The concert will feature a wide variety of A cappella songs from Mozart to Michael Buble.
There will also be performances from local music groups, including school vocal groups.
