Nothing quite compares with the sound of a large music ensemble filling the cracks and corners of a concert hall.

In imitation, audio engineers amplify rock music and movie soundtracks to deafening levels, arranging and rearranging speakers to create "surround sound." But even if decibel levels are the same, there are crucial differences in quality between music played at dynamic extremes, music amplified to extremes, and music that is extremely loud from many, many musicians all playing within normal dynamic levels.

On Friday, the Ninth Annual Hawai'i International Choral Festival convened almost 300 musicians to celebrate the 250th anniversary of Mozart's birth. The multitudes added timbral complexity and depth, but even hair-raising dynamics never deafened; the effect was instead thrilling, powerful, exciting.

The Festival Chorus, arrayed as a dense backdrop to the Hono-lulu Symphony, included the Hamilton Civic Choir from New Zealand, the Merveille Chorus Group and the Osaka Toin High School Music Club from Japan, the Oral Village Ideas Choral Group from Ghana, West Africa, and the University of Hawai'i Chamber Singers, all in addition to the Honolulu Symphony Chorus.

Topping it off were four guest soloists familiar to Honolulu audiences: soprano Alicia Berneche, mezzo-soprano Milargo Vargas, tenor Vale Rideout and bass-baritone Burr Cochran Phillips.

Honolulu Symphony's Chorus Director Karen Kennedy, who announced before the concert that this is her last season with the chorus, conducted the whole, holding the ensembles together, balancing so soloists could be heard, and creating a surprisingly homogenous sound.

Kennedy et al. dedicated the second half of the concert to Mozart's unfinished "Requiem," using the most well-known version, which was completed by Mozart's student, F.X. Suessmayr.

Friday's opening, featuring Paul Barrett on bassoon and James Moffitt and Norman Foster on alto clarinets, set just the right feeling: somber, penitent, expectant and delicately sublime.

"Requiem" unfolded with impressive majesty, a powerful reminder for everyone of human mortality and final judgment: divine judgment for those who believe in afterlife, communal judgment for those who do not.

Friday's performance abounded with memorable passages. One of the most beautiful was the beginning of "Tuba mirum," with a gorgeous solo by trombonist Kirk Ferguson.

The soloists shone, their vocal timbres so different that each remained distinct, yet never clashed, even as a quartet, and each contributed moments of brilliance.

Honolulu Symphony's Assistant Conductor Joan Landry conducted the first half of the concert, beginning with Ibert's "An Homage to Mozart," composed for the 200th anniversary of Mozart's birth, and ending with Mozart's last Symphony, nicknamed "Jupiter," No.41, K.551.

Ibert's "Homage," not widely known, captured Mozart's clarity, but was otherwise pure Ibert. High points included a delicate, captivating solo by flutist Susan McGinn and a trumpet duet by Michael Zonshine and Mark Schubert.

Landry's reading of Mozart's "Jupiter" adhered closely to the score, and each movement emerged from her baton with more assurance. The third movement, with its theme that slides down to be caught by the string basses and timpani, was particularly nice. Only the massive, complex fourth movement showed signs of struggle.

As a conductor, Landry is young but quickly developing a broad repertoire of techniques, such as her upward cutoff to the fourth movement of the "Jupiter," which kept that last, heavy chord buoyant.