The first performance of The Messiah was on April 13, 1742 in Dublin, Ireland. It almost wasn't performed because Handel's music was considered to be "profane and subversive". Jonathan Swift, of Gulliver's Travels and Dean of St. Patrick's Cathedral, didn't want singers from the cathedral to participate.
Swift relented and the performance took place. A year later, Handel premiered a different version of The Messiah in London. Throughout the 1750's Handel tinkered with the score to suit different performers and occasions.
Mozart re-orchestrated The Messiah and included new instruments from the orchestra of the classical period. In the late 1950's, Sir Eugene Goossens re-orchestrated The Messiah and included new instruments from the 20th Century orchestra.
Over the centuries, the performance of Handel's Messiah has been as cosmopolitan as the composer himself. The original performance had a modest orchestra and chorus. There are "sing along" performances of The Messiah with over 3,000 singers.
Most performances of The Messiah fall between these two poles, but which approach is right?
Does it matter? 3,000 singers getting together for a community performance has one value and 24 professional singers getting together for an "authentic" performance has a different value.
This sticking point could be using "authentic" to describe a performance.
With The Messiah we have a difference between the original performance in Dublin and the second performance in London. Handel authorized both versions so which is authentic?
Some might look at a chorus of 200 semi-professionals and think that Handel would be horrified. Maybe. What would Shakespeare think of movie versions of his plays?
When it comes to performing a masterpiece like The Messiah, there is no correct way to do it.
Period performance people, those who would be "authentic" use men on what have become the female parts of soprano and alto.
This is half-baked authenticity. The men singing alto and soprano today still have their balls. A man singing soprano or alto in Handel's day would have been castrated.
To me, that's a monumental difference. It can be wonderful to use men on alto and soprano just don't call it authentic if they're still in possession of the family jewels.
The Messiah works in all its various incarnations.
Here is an approach that favors period performance.
Here is Eugene Goosens' 20th Century version.