What happened between Johann Sebastian Bach and Wolfgang Amadeus Mozart?

Nothing, for starters, because they never met — at least not on this planet. Bach was pushing up daisies six years before Mozart came onto the world. But as both composers are considered by classical music intelligengtia to be the iconic representatives of their respective eras — Baroque for Bach, Classicism for Mozart — the aesthetic mutation from one style to the other can be traced by looking at Bach's legacy — because he kept it all in the family.

And a big family it was for Bach.

Surely anyone culturally in-the-know is familiar with father Bach's musical output — at least some of it. Though many may not know that, as prolific as he was on the staff, he was just as fruitful under the sheets. As a man of god, Bach multiplied.

He had seven children with his first wife, Maria Barbara, his second cousin. Three survived him. With his second wife, Anna Magdalena Wilcken, he had 13 more.

Mercury's "Bach and Sons" concert, set for 8 p.m. Saturday at the Wortham Theater Center, is a musical chronolog from Bach the father through three of his sons. The sequential approach is something guest soloist and leader, French harpsichordist Christophe Rousset, has presented previously.

The program begins with J.S. Bach's Orchestral Suite No. 1 in C Major and time travels with Wilhelm Friedemann Bach's Sinfonia in D Major, Carl Philipp Emanuel Bach's Concerto for Harpsichord in C Minor and Johann Christian Bach's Sinfonia in G Minor — in essence, the "in between," what music historians coin as Galant or Rococo.

"Sometimes I do the same kind of program on harpsichord solo with a J.S. Bach suite and then move through the sons with sonatas," Rousset says. "It's interesting how music changes in a few short years, how the sons attempt to reject their father's aesthetic.

"And you can understand why. I imagine that because J.S. was such a genius, it was probably very difficult to be his son. They tried desperately to find their way, and used the Neapolitan and Galant language to find another form of expression."

It often said that the complex counterpoint, rich harmonies and the drama in the height of the Baroque period had reached its ultimate climax with J.S. Bach such that compositional technique had no choice but to abandon it and seek its complete opposite.

As it pertains to W.F. and C.P.E. Bach there was additional pressure to invent a voice that was uniquely theirs — because no one wants to live in the shadow of a parent. More specifically, W.F. and C.P.E. Bach used new musical structures. They preferred the sonata form, which begins with an exposition, follows with development of themes and ends with a recapitulation of the original exposition, in lieu of the suite, which comprises a collection of contrasting movements.

"The comic element is that they, in turn, influenced their father," he says. "J.S. Bach will write in this language of music for pieces like The Musical Offering."

But for J.C. Bach, who was 14 when his father died, the experience was much different.

"He probably didn't know his father as well because he was too young when his father died, so he didn't have the same pressures of his older brothers," Rousset explains. "You feel more freedom in his music. He wrote opera; his father hated opera. He even converted to Catholicism; his father was Lutheran."

And it's this fresh manner that caught Mozart's attention when he met J.C. Bach in London. Mozart went on to pen three of keyboard concertos after J.C. Bach's chamber music.

The Sturm and Drang (Storm and Stress) movement — think minor keys, angular intervalic leaps, lots of tremolo and the overuse of diminished seventh chords — emerges in the works of C.P.E. Bach shortly after the death of J.S. Bach in 1750. It appears in J.C. Bach's Sinfonia in G Minor and in C.P.E Bach's Concerto for Harpsichord in C Minor.

And in Mozart's Symphony No. 25 in G minor.

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Mercury presents "Bach and Sons" on Saturday, 8 p.m. at Wortham Theater Center. Tickets start at $10 and can be purchased online or by calling 713-533-0080.