I recently went to watch Mozart's The Magic Flute and saw at the orchestra that all the double bassists (I think there were 3 of them) had 5 string basses. I had never seen a 5 string double bass up close before, so it intrigued me. Then I searched some other works performed by orchestras, like for instance:
that also have 5 string basses (not all of them, but still). And this got me wondering:
Is it common for an orchestra to use 5 string double basses or is it preferred to use the normal 4 string ones?