Bernard Labadie is about to undergo the biggest transition of his career. After serving as founding music director of Les Violons du Roy, a period-style chamber orchestra in Québec, since he was a precocious 21-year-old, he is stepping down at the end of this season.

“It’s been 30 years, which is a lot of time, and I’m 51,” he said. “I think it is the right time to make that kind of decision. If wait until I’m 60, I might not be able to do it. And I think it is important that the organization be able to think by itself and reflect upon its future.”

For now, at least, he has no plans to jump to another ensemble. Labadie intends to remain close to Les Violons du Roy and continue as head of its sister choir, La Chapelle de Québec. He also is set to serve as curator of the Toronto Symphony’s Mozart festival in January 2015 and 2016.

But for the most part, he will be guest conducting, something he does a great deal of already, including recent appearances with the English Concert. In that capacity, he returns to the Chicago Symphony Orchestra for a series of concerts May 8-10 with Canadian pianist Marc-André Hamelin.

For Labadie, it has been important to develop strong, ongoing relationships with the orchestras where he guest conducts, because he takes a period-style approach to 17th- and 18th-century programming that quite often differs from the later, more Romantic style to which modern orchestras are accustomed.

“The first time that you work with an orchestra,” he said, “even the best orchestras like the Chicago Symphony, in the repertoire that I do, it’s clear that it’s not their usual fare. It’s a little bit of a crash course in a foreign language. For me, it’s important to go back to these orchestras and build from where we were the last time.”

Labadie acknowledges that he has gotten resistance from certain ensembles that were not open to his approach. “It happens less and less, because people know who I am and, so, if they feel there is no interest by the musicians, they don’t invite me,” he said.

At the same time, he said, orchestras are programming more early works, and they increasingly are open to the period-performing styles that several decades ago were dismissed by much of the mainstream musical establishment. “Most of them now know that it has to be somehow part of their diet at some point,” he said. “First of all, audiences expect it. And the musical world has changed to an extent that these orchestras cannot ignore that [period] movement, simply because that movement now is not only limited to the purely Baroque repertoire. It has expanded to the Classical repertoire and into the early Romantic repertoire.”

For his CSO program, Labadie will not be leading Baroque repertoire with which he is perhaps most often associated. Instead, he built a program around Beethoven’s Symphony No. 1, which was written around 1795 and premiered in 1800. He called the work one of the “missing links” between the purely Classical Viennese style and what would eventually become Beethoven’s mature sound.

“That symphony,” he said, “which is very seldom performed — I’ve always found it one of the most fascinating, because you hear this Haydnesque clarity, but it’s already on a slightly grander scale, the way Beethoven would do things more and more, and you have some of the bold moves that you will hear later.”

Wanting to illustrate a bit of the music-historical journey that led to the milestone piece, Labadie immediately added a work by Haydn, one of Beethoven’s teachers. He chose the composer’s Piano Concerto No. 11 in D major (1779-80), which will feature Hamelin as soloist. The two musicians recorded it and two other Haydn keyboard concertos two years ago with the Les Violons du Roy on the Hyperion label.

Rounding out the program are works by two Classical-era composers who were well regarded in their time but are all but unknown now: Joseph Martin Kraus’ Sinfonia in E Minor and Henri-Joseph Rigel’s Symphony No. 4 in C Minor. Kraus (1756-1792), grew up and studied in Germany and spent most of his career in the Swedish royal court, composing operas and a wide range of instrumental works. Also a German, Rigel (1741-1799) moved to Paris in 1768 and became one of that city’s best-known teachers and composers, writing music in a hybrid style that melded German and French traditions.

To all of these Classical-era works, Labadie will bring largely the same period-performance approach that he would apply to Baroque music. Because the sonic world changed little in the 30 to 40 years between the death of J.S. Bach and a symphony by Kraus, he does not believe it makes sense to perform Baroque music in a period style and then bring a big, Romantic take to the music of Haydn or early Beethoven. “It’s not about being dogmatic, it’s about being coherent,” he said.

That means he will encourage the CSO musicians to perform with cleaner textures and a leaner sound, which means less vibrato, greater contrasts and for the string players, more attention to bow speed and its effect on musical expressiveness. In Beethoven’s Symphony No. 1, Labadie will insist on sticking to the often quicker tempos indicated by the composer’s metronome markings, which many later conductors have discounted as somehow mistaken — an idea that Labadie dismisses as “complete baloney.” “These are things that I hope will be clearly audible for the audience,” he said.

Although Labadie believes strongly in a period-performance approach to the music on the CSO’s upcoming program, he is quick to acknowledge that it is not only legitimate way to do it. “The last thing I would do is to make people believe that the longstanding tradition of Beethoven with great orchestras like the Chicago Symphony is wrong and should be completely redone,” he said. “I just want to bring to the table a different and yet entirely valid proposition — valid I hope not only historically but musically.”

Wherever Labadie’s future career path takes him, he is sure of at least one thing: There will be no change of residence.

“I’m very much a Québec boy,” he said, “and there is no plan whatsoever to move.”

Kyle MacMillan, former classical music critic for the Denver Post, is a Chicago-based writer.