The summer's biggest music event — the two-day KCCN FM100 Birthday Bash 18 — will unfold at 5:30 p.m. July 25 and 26 at the Waikiki Shell with the usual pomp and circumstance: a lot of powerhouse Island sounds, including the return of New Zealand's Katchafire.

There'll also be a new wrinkle this year: the Diamond Head Greens, makai of the Shell's lawn seating area adjacent to Kapio'olani Park, which will create a mini-festival beer garden environment with food and beverage booths, exhibits and talent appearances at fan a fan appreciation table.

Bud Light is the major sponsor this year, and a sellout again is anticipated, with two different programs each night.

"Coming to the Bash has been so much more than just seeing the bands on the stage," said Davey D, FM100 program director. "It's been a lifestyle celebration ... the festival garden will enhance the 'ohana feeling that has grown up around this event. It will reinforce the celebratory atmosphere that we've come to love."

The musical lineups:

• July 25 — Katchafire, Kapena, Ekolu, Koauka, Rebel Souljahz, B.E.T., Beach 5 and Laga Savea.

• July 26 — Fiji, Katchafire, Natural Vibrations, The Mana'o Company, J Boog, Na Wai Wai Ho'olu'u o Ke Anuenue, Kawao and the Battle of the Bash winner.

The first 5,000 patrons through the gate each night will receive a free FM100 Birthday Bash bag only available at the concert. Those in reserved seats will receive a Love's Bakery seat cushion.

Doors open at 4 p.m.

Tickets: One show, $17 for lawn seats before July 1, $24 thereafter; $18.00 for terrace; $26 after July 1; pool seats, $38; for two shows, $34 for lawn, $36 for terrace, $38 for pool seats; two-night discount not available for prime pool seats.

Reservations: 877-750-4400, www.ticketmaster.com.

Information: 591-2211, http://kccnfm100.com.