When the Emerson String Quartet was in Ann Arbor early last December, it played Haydn, Beethoven, and Shostakovich. When it returns to town on Sunday, September 26, it will play Tower, Beethoven, and Shostakovich.

From the Emerson’s choice of repertoire, two things are instantly apparent. First, there is the implied equivalency of Haydn and Tower; second, there is the stated centrality of Beethoven and Shostakovich. This is not to say that the Emerson’s musicians regard a string quartet by the father of the string quartet and a string quartet by the grande dame of contemporary music as equivalent. Rather, just as they honor Haydn by continuing to perform his quartets, they seek to honor Tower by presenting her Incandescent, which they premiered in 2003.

But the quartets of Tower and Haydn are not central to the repertoire of the Emerson Quartet in the way Beethoven and Shostakovich quartets are. The Emerson has recorded complete cycles of both of those composers’ quartets and has performed both concerts and concert series dedicated to them. Beethoven and Shostakovich are central to the repertoire of every string quartet — but to the Emerson, Beethoven and Shostakovich are heroic composers.

Shostakovich composed his A Major String Quartet in the last year of what Russians call the Great Patriotic War, and it shares with his “war” symphonies an incredible intensity, a tremendous expressivity, and an indomitable will. Beethoven composed his C-sharp Minor String Quartet in the last years of his life, and it resembles his other late quartets in its overwhelming concentration, overpowering spirituality, and irresistible urge to rise above the limits of this life. From the huge sonorities of the opening movement to the enormous lines of the closing movement, Shostakovich’s A Major Quartet is a monument to suffering, strength, and endurance. From the melancholy fugue of the opening movement to the convulsive rhythms of the closing movement, Beethoven’s C-sharp Minor Quartet is a tombeau to hope, an adieu to life, and a hymn to transcendence.

The Emerson’s recording of Shostakovich’s A Major Quartet is a shade mannered and a little forced, and its recording of Beethoven’s C-sharp Minor is a bit lethargic in the slow movements and a tad rushed in the fast movements. But the group’s previous local performances have often been both more technically exciting and more interpretively convincing than its recordings. One could reasonably trust that the Emerson’s performances of Tower, Beethoven, and Shostakovich here this month will be as just as exciting and as convincing.