When Mozart fashioned his own version of Handel’s Messiah and prepared to mount it in Vienna, Austria, he was confronted by a dearth of talented trumpet players, and so scored the solo passagework for “The Trumpet Shall Sound” for French horn instead. Robert Mealy, first violin and guest director of the New York Collegium, used this story Friday evening at the Church of St. Vincent Ferrer to illustrate the decline of musical life in Vienna in the period just before Haydn and Mozart and to underscore the prior brilliance of the years of the mid-17th century under music loving emperor Leopold I. In a fascinating program, the Collegium players presented music in a variety of styles from those glorious early days.

With fame being a relative term, the most famous of the evening’s composers was Heinrich Ignaz Franz von Biber, the great violinist of Salzburg. Sonata X a 5, a ruminative and stately piece, tinged with what Mr. Mealy described as “South German melancholy,” is from the collection “suitable for court or chapel” and features a long-bore trumpet. Somehow the combination of improvisatory style, reflective sadness, and brass ascendancy reminded me of a slow jazz ballad — the unusual harmonies of the period before welltempering had just a hint of the Chet Baker to them. Quite a surprise in a concert of music well over 300 years old.

In complete contrast was the work of Johann Heinrich Schmelzer, longtime kapellmeister for Leopold at the Imperial court. Sonata con tribus violinis is stereotypical Baroque music as understood by modern untrained ears. It could easily have been written by virtually any Venetian composer between Gabrielli and Vivaldi, and falls squarely into the pleasant, toetapping camp. More substantive was the Serenata con alter arie, a compendium of entertainments for the royal enjoyment, complete with commedia del’arte characters — there is an entire section titled “Erlicino.” It also features punctuation marks like foot stomping written into the score. Delivered by these otherwise scholarly practitioners, such details emphasized the music’s rough, primitive qualities.

All of this music was extremely well played and proved we were in the presence of devoted students of an arcane art. But some adjustments must be made in the modern ear, especially to compensate for the natural equivocalness of the brass instruments. In Sonata a 3 from Prothimia suavissima by Antonio Bertali, trombonist Greg Ingles did a heroic job of attempting to hit all of the myriad of notes written into his ecstatic runs, but could not possibly have enunciated each and every one. Either audiences in the 1670s did not expect perfection or there was some race of super beings performing in the Holy Roman Empire, who subsequently disappeared sometime between Bertali and Mozart.

Other composers on the program, including Romanus Weichlein and Phillip Jakob Rittler, were described by Mr. Mealy as even more obscure. One interesting work of a different character was an organ solo by Johann Caspar Kerll, whose improvisatory and gentle style was captured lovingly by Eric Milnes, who also provided harpsichord continuo for many of the other pieces.

But the biggest surprise at this event was the large number of patrons for such esoteric music. The church is quite large and most every seat was full. There was a preponderance of men in sport coats, each with very long hair tied up in ponytails, a hirsute style that matched several of the performers. Are they a subculture of devotees who simply blend into the quotidian New York atmosphere or are they more secretive and focused, like Bradbury’s “book people,” desperately striving to keep a forgotten art form alive through a dark age?