Felix Mendelssohn Bartholdy was, like Johann Sebastian Bach, one of the great German composers. He adored Bach and it's not opinion but fact, that without this musician Bach's music probably wouldn't have "survived". He was the one, who after a period of over eighty years brought back the uniqueness of the work of the composer from Thuringia to mankind.
Here is where you can explore more about Felix Mendelssohn Bartholdy and among other composers you will find interesting websites about this artist too.
However, just in brief, accidentally at the time of the death of Johann Sebastian Bach the taste for music of the back then epoch changed dramatically and Bach's work wasn't exciting for the public taste anymore. His works was never physically lost, but just nobody was interested to listen to it from the time of his death. That wasn't true for musicians of the following generations. They all knew Bach well and they knew about his brilliance. But the public, that had no interest for over three generations.
Felix Mendelssohn Bartholdy was excited by Bach's work in general and by Bach's St. Matthew Passion in particular. He was so much excited that he arranged a shorter version compared to the original. Because he believed he couldn't expect the audience to listen to the original length. He performed this, his version exactly one hundred years after its debut performance. Later research in the Bach science found out, that the St. Matthew Passion originally was performed one year earlier compared to what they believed before. So Bach Science had to change the distance to the date of the revival by Felix Mendelssohn Bartholdy as well. So actually, he revived the St. Matthew Passion one hundred one years after the initial date. The audience was excited and it's crystal clear, that you may attribute the degree of respect and the high profile to this special event and evening. Like one hundred and one years ago, it was precisely the same day in the year. Good Friday.
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