BOCA RATON —He mapped out an Old World pastorale in the Elgar, taking a spin through the English countryside. She led you across a New World dance hall with the Piazzolla, a spin-off on an Argentine ballroom. If both have roots in folksy traditions, performed by strings only, the last word was aristocratic and full-scale: Mozart's final symphony.

The Boca Raton Philharmonic Symphonia continues to blossom in programming, performance and audience building. Sunday afternoon, returning guest conductor Giancarlo Guerrero encouraged the 40 musicians — especially the 24 string players — to dig deep for a fuller, more thrilling sound in Boca's Roberts Theatre at Saint Andrew's School.

The bigger sound put violin soloist Bella Hristova at a disadvantage a few times. Still she spoke up fluently in Las Cuatro Estaciones Porteñas (The Four Seasons of Buenos Aires), Piazzolla's answer to Vivaldi's Four Seasons — tango-style.

The major work for solo violin and strings is a healthy break from the usual concerto. Plus there's humor as Piazzolla quotes and comments on several celebrated Baroque tunes, including the Pachelbel Canon in D and the Vivaldi.

In quicksilver moods, Seasons flashes from thunderstorm to tender heartbreak. The 20-year-old Bulgarian-born soloist complied with remarkable sweetness, then earthiness, even dark cries of the soul. Despite the flip-a-coin changes in tone and temperament, Hristova wrapped it together smoothly with subtle musicianship and sensitivity. Even in Piazzolla's edgy, percussive special effects, Hristova made music.

A student of Ida Kavafian at Philadelphia's Curtis Institute of Music, Hristova charmingly accepted three curtain calls and an ovation.

The Piazzolla also brought out gutsy accents from the string orchestra — the advantage of having on the podium a percussionist by training. Guerrero, Nicaraguan by birth and raised in Costa Rica, has also conducted in Buenos Aires. The oomph he packed into the four tangos was only one reason the Eugene (Ore.) Symphony music director has been invited twice in Boca's two seasons.

Elgar's Serenade for Strings glowed with a sunny, yet gentle lilt from well-shaped phrases, an unhurried pace, plus an intimacy that approached chamber music. In Mozart's Symphony No. 41 (Jupiter), Guerrero pressed well-thought-out, often dramatic concepts to their inexorable finale.

Sunday's performance by the Boca Symphonia with Guerrero and Hristova will be broadcast on WXEL-FM 90.7 at 8 p.m. Feb. 21.