Spend a Sunday afternoon with two of the premier composers from the 18th century Vienna when Pennsylvania Sinfonia Orchestra presents “A Viennese Afternoon,” 4 p.m. Feb. 23, Christ Lutheran Church, Allentown.

Enjoy the music of classical composers Mozart and Haydn in an intimate program that marks the Sinfonia debut of Bethlehem native and Lehigh Valley Charter Arts High School graduate Fiona Gillespie singing the soprano solo on Mozart’s “Exsultate, Jubilate, K. 165.”

Corliss Bachman, Pennsylvania Sinfonia Orchestra Executive Director, says Gillespie, whom she describes as a “brilliant soprano,” was supposed to debut last winter but a snowstorm cancelled the performance, the first time the Sinfonia had cancelled a concert in its 37-year history.

Bachman says she’s thrilled to have Gillespie back and that her voice is “well-suited” for Mozart’s motet with its triumphal final aria “Alleluja,” the most well-known section of the piece.

Bachman says the Sinfonia’s concerts of chamber music by a small intimate ensemble have been popular and the afternoon setting has also been well-received.

She says Mozart and Hayden were contemporaries in Austria in the mid-18th century, and the older Haydn was a mentor to the younger composer.

Haydn was instrumental in the development of chamber music and for much of his career he was the most celebrated composer in Europe.

Bachman says the concert marks the first time that the Sinfonia is performing Haydn’s “Symphony No. 78 in C minor.”

“It’s just something we never got to before, not that it’s not worthy,” she says.

She says the symphony is one of a trio of symphonies, Numbers 76, 77 and 78, for a planned trip to London, which never happened.

“It shows a maturity and stylish polish that highlights Haydn’s symphonic mastery,” Bachman says.

Haydn scored the symphony for two violins, viola, basso, two horns, two oboes, one flute and one bassoon, perfect for the 21-member Sinfonia ensemble.

Bachman says that Haydn was 50 when he wrote the symphony, however the influence of his friendship with Mozart is evident in No. 78, the first movement of which bears a thematic resemblance to that of Mozart’s “Piano Concerto in C minor, K491.”

In contrast, Mozart was in his teens when he wrote “Exsultate, Jubilate, K. 165” and his other piece being performed, “Divertimento in D for Strings, K. 136.”

“His talent is really quite astounding,” says Bachman.

Divertimentos were usually composed for a smaller ensemble, also making it a good choice for the Sinfonia. “Divertimento in D, K. 136” was one of three composed for string orchestra by Mozart in Salzburg in early 1772.

“Exsultate, Jubilate, K. 165” is a religious solo motet composed when Mozart was staying in Milan in 1773. He originally composed the piece for the castrato Venanzio Rauzzini, who gave the first performance of “Exsultate” in Milan. Today, the solo is sung by a soprano and has become a favorite piece of repertoire for soloists. It too was written for a smaller ensemble.

“The repertoire we play is suited to our size orchestra,” Bachman says. The Sinfonia includes instruments for all the parts: strings, flute, oboes, horns, bassoon and organ.

Bachman says that Gillespie, who has developed a reputation in the Lehigh Valley for her “brilliant sound” and “silver tone,” has also sung solos for the Bach Choir of Bethlehem. She is on the music faculty at Muhlenberg College.

Tickets: at the door, Christ Lutheran Church, 1245 W. Hamilton St., Allentown; PASinfonia.org; 610 434-7811. Tickets for those 62 and older are available. Students are free. A limited number of economy tickets for any age is available for seating in rear rows and must be ordered by phone by the Friday before the concert. Free parking is available in the church parking lot across street. After the concert, the audience is invited to meet the musicians at a reception.