Musicians aged 14 to 17 featured in the Rock on the River concert at Caroline's Boatshed Bar & Eatery on January 5.
"They're our tomorrow," owner Caroline Norton said.
The concert is part of a series. Her Bring on Summer concert at Labour weekend was "packed to the seams".
Sunday's event took place on a windy afternoon, with listeners sitting on a veranda and outside the Whanganui hotel, and bands on a stage on the back of a truck.
The young bands were Rhythm Vision and In Business, both made up of Whanganui High School students.
They were encouraged by teachers Fred Loveridge and Brent Holt, who did the technical sound.
"They get stronger and stronger the more live performances they do. We are pushing for them to do as many as possible," Loveridge said.
Rhythm Vision is usually three people, but bass player Imogen Maguire was away. Guitarist, pianist and vocalist Dan Goodwin said her bass had been loaded onto the backing track they planned to use.
Goodwin, aged 17, writes the band's material, with additions from Maguire and 15-year-old drummer Chester Nevil.
They played one cover - Pressure, by Muse, and the rest of their set was original.
Goodwin and Nevil want musical careers, while Maguire is headed for the arts. The trio will be releasing an album this year, which will be available digitally on Spotify.
They can also be found on Instagram as rhythmvision_nz.
In Business was the regional winner of SmokefreeRockquest 2019, in June. It consists of drummer Max Hughes and singer Faith Solomona, both 15, with bass guitarist Tomas Bidgood and guitarist Christian Garratt, both 14.
Rockquest judge Estere Dalton said the four had a strong energy and worked well together.
On Sunday they played the cover Where Is my mind, by The Pixies, and their own material.
Hughes said they were not nervous.
'We gig most weekends so it's just kind of second nature."
Their song of the moment is their newest, titled Boy.
"It's about a girl who has a crush on a guy who's really toxic and naughty to other people, a bully," Solomona said.
The group intends to competein the rockquest again this year - and win if possible.
Both young bands played in the Hinengaro Rangatahi Festival at Majestic Square on December 13. They will perform again on January 11 and 12 at Welcome to Nowhere, a ticket-only festival held "in a beautiful secluded location somewhere near Whanganui".
It's organised by Wellington's Eyegum Music Collective, and tickets can be bought online.
The third band in Sunday afternoon's Whanganui concert was Loveridge's well-known Whiskey Mama, with vocalist Kerry O'Sullivan.