“This song is called ‘You Never Loved Me’ — it’s another cheery, optimistic number,” says Aimee Mann, introducing the second of four songs in this Tiny Desk Concert. She has been writing songs on the human condition — more often than not with a strong sense of humor to underpin the inevitable melancholy — as far back as the ’80s, when she was the singer and bassist in Boston’s The Young Snakes. Mann’s newest solo record, the first in five years, is baldly called Mental Illness — clearly, there’s a deep honesty within these songs.