Florence Foster Jenkins. (Spoilers below!)
On one level a light tragi-comedy about a rich woman who realises her dream to sing opera at Carnegie Hall, overcoming her (total) inability to sing (at all) by her sheer love of music.
On another level, it's a one joke comedy where laughs come at the expense of a deluded old lady who is duped by a bunch of yes men into thinking she is good enough to sing opera at Carnegie Hall and then is surprised when everyone laughs at her.