Mendelssohn was influential from the time he was 17 until many years after his death in 1847. Aside from his own music, he led the first public performance in 100 years of J.S. Bach's St. Matthew Passion, which helped spawn renewed interest in the music of Bach. A guiding force behind the founding of the Leipzig Conservatory, he turned the Leipzig Gewandhaus Orchestra into one of the best ensembles in Germany.
The persistent view that Mendelssohn was a lightweight is, rightly, coming in for reassessment. He certainly ranks among the greatest 19th-century composers: Mendelssohn's peers wanted to sound like him, and his was considered the style in which to write romantic music.
The way in which a scherzo movement was composed, for instance, was forever changed under Mendelssohn's influence — particularly his light, elfin writing for the strings, his beautiful use of the woodwinds and the scurrying, fairy-like atmosphere he created. You can hear it in his early Octet for strings; he did it again in A Midsummer Night's Dream and he did it, finally, in his Symphony No. 3, or "Scottish Symphony" — three scherzos that paved the way for a whole century's worth of scherzos.
The marvelous Swiss conductor Peter Maag displays a special feel for the Mendelssohn sound in his 1960 recording with the London Symphony Orchestra (listen at left); the recording captures wonderful chemistry between him and the group. In the concluding movement of the Third Symphony, for example, listeners hear a grand, majestic march down from the Scottish Highlands. You can imagine the gathering of the clans, with everyone in kilts — it's a huge, processional kind of music. It's Mendelssohn at his best, which is saying a lot.