We all have them. Those tried and true numbers we listen to again and again, sometimes over decades.
Whether they were on a mixtape or a Spotify playlist, most of us can recall a time when sad songs were the only ones we wanted to hear.
Funnily enough, it's when we're already sad that we're more likely to turn to them.
Logic might suggest we should switch on something upbeat and happy to counter our mood.
But the heart wants what the heart wants, and sometimes what it wants is Whitney Houston's 'I Will Always Love You'.
Mind you, there's something faintly ridiculous about many sad songs.
If there's even a whiff of insincerity about them - cheesy chords or cliched lyrics - they can move from sorrowful to laughable in a heartbeat.
But then there are the ones that seem to speak straight into your soul.
Lyrics account for some of that - those of us who remember every word of our 'break up songs' could probably still explain how they perfectly described our broken hearts. (Linger by The Cranberries and Ghost by the Indigo Girls, for the record. And now you know exactly how old I am.)
But then there are the songs that defy explanation - Silent Night does it to me EVERY TIME. Minor chords and slow tempo are partly to blame, but perhaps there is a human response to music that is innate and practically universal.
If you doubt me, just Google 'babies crying to sad songs'. You will not regret it.
But back to the reason we turn to them in the first place.
Like massaging or stretching a strained muscle, the kind of pain a good tear-jerker can evoke feels almost pleasurable.
And, like massage and stretching, it's similarly healing. Apparently, hormones like oxytocin are released when listening to sad music that - counter-intuitively - improve our mood.
As Elton said: "It feels so good to hurt so bad/ And suffer just enough to sing the blues."