Surprisingly Gentle Song

So, you have a band. They have a tendency to need to be Careful with That Axe. Their songs tend to be loud, aggressive, hardcore. Whether they lean toward Three Chords and the Truth or Epic Rocking, they are The New Rock and Roll. Moral Guardians hate them. They go crazy with the guitars, they go wild on the drums, the music is always played at top volume...

Wait, what? A slow, quiet, gentle piece? Beautiful and soft, it may be heartwarming or heartbreaking, but the defining characteristic is that it is far less aggressive a piece than you would ever expect from this band. May be a Black Sheep Hit, but differs from that trope in that it's not necessarily a hit, and only applies to normally aggressive bands. Compare Playing Against Type and Scary Musician, Harmless Music.

Examples:

 * The Red Hot Chili Peppers have quite a few of these, for example: "If", "Porcelain", "This Velvet Glove" (to an extent), "Dosed", "Breaking the Girl", and "Under the Bridge".
 * Early in their career they were this trope, with things like "Grand Pappy Du Plenty" and "Lovin' And Touchin'". Now however, they pretty much do this style of song all the time.
 * AFI's "The Leaving Song" on Sing The Sorrow, and "The Interview" on DECEMBERUNDERGROUND. Same applies to most of "Morningstar" on The Art of Drowning and the verses of "God Called in Sick Today" on Black Sails in the Sunset.
 * The Red Jumpsuit Apparatus's first album had "Cat and Mouse" and "Your Guardian Angel".
 * They're hardly a very hard band to begin with, but a diabetes-flavored love ballad like Your Guardian Angel coming from any semi-hard rock band is pretty surprising.
 * Slipknot's "Vermillion, Prt. 2" and "Circle".
 * and more recently "Snuff".
 * Metallica's "Nothing Else Matters".
 * This was preceded by Fade to Black, Welcome Home (Sanitarium), and One; and followed by The Day that Never Comes
 * And don't forget "Low Man's Lyric".
 * Scary Kids Scaring Kids has "Watch Me Bleed".
 * Megadeth's "Promises", which is a beautiful power ballad, complete with string arrangements and being based around a Romeo And Juliet theme. If someone else was singing it, you would never know Dave Mustaine had written this song.
 * "Beth" by Kiss.
 * Same goes for Forever and We Are One
 * "Three Shadows, Part I" from Bauhaus' third album, The Sky's Gone Out.
 * J-Rock band Chatmonchy is normally known for upbeat songs that are heavy on the drums and guitar like "Hana No Yume" - except for a slow piano-and-vocals piece called "Sunao."
 * "The Garden of the Goddess" by Galneryus
 * "Ares's Lament/"So Lonely," "The Love Of My Life," and "Never Change Your Mind" by Loudness
 * "Wake Up Honey" and "Thanx Givin Day" by Miyavi
 * "Serenade", "Love will be born again" and "Episode" by Versailles.
 * "Forever Love" and "Tears" by X Japan
 * Tenacious D's Fuck Her Gently.
 * The Velvet Underground pulled an entire album of this with The Velvet Underground.
 * Similarly, The Jesus and Mary Chain, famous for ear-splitting feedback and concerts that ended in violence, did this with the albums Darklands and Stoned and Dethroned.
 * "Good Riddance (Time of Your Life)" by Green Day. And before mention it--yes, it is a breakup song, but it's still melodically fitting, and, for a breakup song, it's surprisingly kind. "I hope you had the time of your life..."
 * "When It's Time" by the same band.
 * "Hello" and "My Immortal" by Evanescence, although the radio edition of the latter ends off with a harder sound. (Link to the album version for that reason).
 * "Swimming Home" is this to their Self-Titled Album and "Good Enough" is this for The Open Door.
 * "Gasoline" by Moist, for you Canadians.
 * Rammstein often has one toward the end of an album: e.g. "Roter Sand", "Nebel", "Ohne Dich" and "Ein Lied."
 * "Heal" by Buzzov-en from At a Loss. They're a Sludge Metal group. This is probably the only non-angry song in their entire discography. (If the Wiki Magic could cough up a link, that'd be great.)
 * Linkin Park tends to have one or two of these per album, ranging from "My December" to "Iridescent".
 * Dragon Force (video game) has one slow song per album in between all the blazingly fast Power Metal: "Starfire", "Dawn Over a New World", "Trail of Broken Hearts", "A Flame for Freedom", and an acoustic version of "Seasons".
 * The Grindcore band Anal Cunt had an entire album of surprisingly gentle songs called Picnic of Love.
 * "In Vino Veritas II" by A Wilhelm Scream.
 * "The Vulture Act I" by Gallows.
 * "Speak My Name" by IQ.
 * Sabrina by Inkubus Sukkubus
 * Pantera's cover of "Planet Caravan" by Black Sabbath - enough so that the Far Beyond Driven liner notes include a short message from Phil Anselmo explaining to fans (who might not be familiar with the original) that they're just covering a song they like, not attempting to have a pop hit.
 * The Black Sabbath version itself also qualifies - While Ozzy was singing, their albums almost always included a token ballad like "Changes" and/or a short, pretty acoustic instrumental like "Orchid".
 * Pantera themselves are not immune to writing gentler songs, "Cemetery Gates" is Pantera's attempt at a Power Ballad and Suicide Note Part 1 is extremely subdued and depressing.
 * The Who, normally known as "The World's Loudest Rock Band," have a touching ode to the Anti-Villain called "Behind Blue Eyes."
 * A well-known example is Rise Against having the all acoustic "Swing Life Away," and "Hero of War".
 * Not to mention 'Roadside'
 * "The Last Man On Earth" by Schoolyard Heroes.
 * "Metaphor" by In Flames is an example of them writing an actual gentle song rather than the folk passages they used on early albums to give the listener's a break. Gentle, understated, melancholic but very bitter and resentful lyrically.
 * They also have "Come Clarity". "Take me somewhere/don't wanna live/in this dream one more day."
 * "The Bard's Song" by Blind Guardian qualifies with its medieval folk sound contrasted against the blazing, speedy, Power Metal sound they normally have.
 * They tend to have one per album; there's also "A Past And Future Secret," "The Eldar," (except for the Metal Scream) "Harvest of Sorrow," "Skalds and Shadows" and "War of the Thrones".
 * Bad Brains have some, mostly due to their reggae influences coming to the forefront: Their self-titled album, for instance, consists of Hardcore Punk interspersed with a few down-tempo reggae songs ("Jah Calling", "Leaving Babylon", and "I Love I Jah" specifically).
 * Opeth's "Benighted".
 * Opeth have quite a few of these songs. "Hours of wealth," "Isolation years," "Face of Melinda," "Silhouette" and "Burden" are all examples. Also, the entire "Damnation" album.
 * Shadows Fall has "Another Hero Lost", which was written in memory of a dead relative of Brian Fair's that died in Iraq. There's also the acoustic instrumentals that the band always includes once per album.
 * Flyleaf, while not a loud band at all, has had a few songs that are dramatically more calmer and quiet then their usual songs. Mostly in their first studio album.
 * The Dillinger Escape Plan have included a few more accessible songs off their more recent albums. They're still very experimental and innovative but make better use of their singer's clean vocal range (something their first singer didn't have.) Tracks like Unretrofied, Black Bubblegum & Milk Lizard sound akin to something a more agressive Faith No More might write.
 * "Come Away Melinda" on Uriah Heep's first album. Especially since the rest of the album is Very 'Eavy (and very 'umble). It's also this song that made them become Uriah Heep (having gone into the studio as a band called 'Spice' and using a session keyboardist on the track made them realise they needed a permanent keyboadist, which led to them changing their name to Uriah Heep)
 * Glassjaw, normally an extremely loud and aggressive band, has two of these songs on their El Mark Digital EP. "The Number No Good Things Can Come Of", a piano and drums piece, and "Oxycodone", a Lounge-sounding tune with the lead vocalist singing in improvisation.
 * And now, their latest work, "Daytona White" and "Stations of the New Cross" also count. In fact, most of their Coloring Book album (from which these two songs come from) is this compared to some of their previous work.
 * "Louder Than Thunder" by The Devil Wears Prada, sung entirely by guitarist/clean vocalist Jeremy Depoyster.
 * The last two tracks off of the album Abducted by Death Metal band, Hypocrisy, are mellow Pink Floyd-esque Progressive Rock tracks. This is in sharp contrast to the rest of the album and their discography.
 * Dream Theater's "Vacant" is the Surprisingly Gentle Song off of Train of Thought, which is an 8+ on the Mohs Scale of Rock and Metal Hardness, since it's slow and melancholy, and just piano, cello, and vocals.
 * Kyuss has "Space Cadet" on the Welcome to Sky Valley album, where it comes between the much heavier "100" and "Demon Cleaner", though Demon Cleaner's still a tad lighter than the rest of the album.
 * Showbread has "The Missing Wife". "Matthias Replaces Judas" starts off as one of these, but gradually builds up in intensity.
 * Epica has "Delirium", "Solitary Ground", "Tides of Time", "Trois Verges" and "White Waters".
 * "Lead Sails (And A Paper Anchor)" by Atreyu.
 * "Tears Go By," "Dandelion," and "She's a Rainbow" by Rolling Stones
 * The Melvins are largely associated with grunge and sludge metal, but have a few gentle songs in their repertoire: "Black Bock" is lightly psychedelic folk-rock (albeit with some serious Lyrical Dissonance). The Crybaby includes a pair of straight country covers featuring Hank Williams III (Hank Williams' "Ramblin' Man" and Merle Haggard's "Okie From Miskogee"). And "PG x 3" is an eerie, mostly a capella version of the folk song "Peggy Gordon", inspired by it's use in The Proposition.
 * Lady Gaga: "Brown Eyes", "Again Again", and "Speechless"
 * "Eh Eh (Nothing Else I Can Say)" is much calmer than her normal style.
 * Don't forget "Fooled Me Again (Honest Eyes)", which was actually pulled from The Fame because she thought it was upsetting the the albums central theme
 * "You and I" is this on Born This Way...
 * Judas Priest: "Angel," "Lost and Found," "Before the Dawn," "Epitaph", "Last Rose of Summer"
 * Bad Religion: "Million Days" off of the Canon Discontinuity album Into the Unknown.
 * "Slumber" from Stranger Than Fiction may also qualify - it resembles an alternative rock song of the loud-soft-loud variety more than it does a Power Ballad, but the verses are surprisingly soft.
 * Angel Beats! anime band, Girls Dead Monster, usually plays loud and hard (as part of their band's 'distraction creating' intent, but many of their songs do have a quieter version on CD.
 * The original band leader pulls this off the best with her final song with a ballad played on a special acoustic guitar, instead of her normal. My Song
 * Danzig's Sistinas. While it's technically credited to Glenn Danzig & The Power Fury Orchestra, there's also "You And Me", from the soundtrack to Less Than Zero. Both are Roy Orbison-influenced ballads that show off Glenn Danzig's crooning vocal style, rather than the dark metal he's commonly associated with.
 * "Darkness" by Disturbed, a soft, acoustic dirge with a cellist section of all things. This from the band who an album earlier provided the world with "No, Mommy! Don't do it again!".
 * Even though it's much heavier, "Overburdened" would count as well.
 * A few of the Paper Chase's songs depart from their usual highly confrontational noise-rock/post-hardcore approach in favor of more melodic, introspective songs, though titles such as "Out Come the Knives" and "At the Other End of the Leash" show that the mood isn't necessarily any different.
 * "Lost in You" by Three Days Grace is a little different from their normal sound to say the least. While the recent album was quite a bit softer than previous ones, this one still stands out.
 * The point of the Colma album by Buckethead was to give his mother something calming to listen to while recovering from illness. Thus, it is a dramatically different sound from his usual stuff.
 * Eminem has a few. "Mockingbird", "When I'm Gone", etc.
 * Metalcore band Demon Hunter seems to pile on more and more of these with every album, but they'd be hard pressed to top their first notable one, the EPIC Tear Jerker "My Heartstrings Come Undone".
 * Underoath are usually placed around Level 7-8 on Mohs Scale of Rock and Metal Hardness. But of course, being a Christian band, have a good number of these spread across their discography. Most notably, "Some Will Seek Forgiveness, Others Escape" and "Too Bright To See, Too Loud To Hear". These were sung almost entirely by former drummer and clean vocalist Aaron Gillespie, with occasional peppering in by screamer Spencer Chamberlain.
 * Gentleness is hardly a surprise coming from Christian Rock band Disciple nowadays thanks to Lighter and Softer, but "After The World" and "No End At All", both tender "God Is Love" Songs, stuck out like a sore thumb on their mostly heavy album Scars Remain.
 * "Flower Sun Rain" by Japanese Doom Metal band Boris is very relaxing until the very end, when it builds into a scorching guitar solo accompanied by heavy drum fills.
 * Portrayed in Spinal Tap with "Lick My Love Pump," Nigel's unfortunately named classical piano piece.
 * Me Without You's Catch For Us Foxes, after eleven tracks of blistering and screaming soundscapes, concludes with "Son of a Widow", which is rather quiet and tender.
 * The Hives are mostly known for high speed garage rock, but their album Veni Vedi Vicious throws in "Find Another Girl", a pretty faithful cover of a 60's R&B ballad by Jerry Butler. It sticks out quite a bit in the middle of the album.
 * Christian Metal band East West's Black Sheep Hit "She Cries."
 * Power Metal bands usually feature at least one ballad per album.
 * Modest Mouse, whose songs typically consist of shrieking existential crises in the form of really elaborate metaphors, also produced "Little Motel," a sober reflection after the loneliness "earned" after destroying a relationship.
 * "Acrid Placidity" by Meshuggah of the album Future Breed Machine. However, the song is still extremely off-putting.
 * System of a Down's "Lonely Day" is considerably softer than their usual style.
 * Black Label Society has Spoke in the Wheel, a very mellow and depressive song that contrasts with other songs sung and composed by bearded, foul-mouthed, pinch-harmonic-crazed Zakk Wylde.
 * The Black Label Society album Hangover Music Vol. VI' is made up mostly of softer songs that utilize acoustic guitar and piano, meaning that the album really is good music to listen to while hungover.
 * "In This River", from their Mafia album, was a quiet ballad Wylde dedicated in memory of Darrell Abbott (he'd actually written it months before Abbott's death.
 * Akercocke has a few parts with clean vocals in their otherwise extremely heavy blackened death metal, but the last song off the album Antichrist - Epode - is fully mellow, beautiful (and is about Satan himself.)
 * "Spit on a Stranger" by indie rockers Pavement is a ballad (albeit a rather bizarre one) from a band who usually did uptempo songs with Word Salad Lyrics.
 * Godsmack have "Serenity" off their Faceless album.
 * Jimi Hendrix had "Castles in the Sand", "The Wind Cries Mary","Sweet Angel", and "Little Wing".
 * "More Than Words" by Extreme, which ironically is their biggest radio hit.
 * Nine Inch Nails did this every now and then, considering that the usual sound of the band is industrial metal. Examples include "A Warm Place", "Lights in the Sky" and "Every Day Is Exactly the Same."
 * The Christian Hard Rock Band RED tends to have at least two per album, beginning with 'Pieces', and 'Already Over (part 2)' in "End of Silence," 'Take it all away' and 'Nothing and Everything' (Which is an alternate version of the opening song 'Fight Inside') on Innocence and Instinct. While they aren't as intensely loud or grating as bands such as Devil Wears Prada, RED is loud enough to warrant these songs being Surprsingly Gentle.
 * Motorhead, a band commonly known for being one of the rowdiest, loudest, crudest bands, released a song titled "1916", a slow, mournful song about a young man being killed in battle in World War 1.
 * A number of Black Metal bands do these, particularly as ambient interludes, intros, or outros. Burzum is a particularly influential example.
 * Progressive Death Metal band Opeth has several examples, including "To Bid You Farewell", "Credence", "Epilogue", "Benighted", "Face of Melinda", "Harvest", "For Absent Friends", several others, plus the entirety of Damnation and Heritage, both of which qualify as Surprisingly Gentle Albums.
 * Big & Rich. Their music is country turned Up to Eleven and beyond, and even most of their ballads are loud and flashy. But each of their albums had a softer song: "Drinkin' 'Bout You" on the first (a barroom shuffle), "I Pray for You" and "Never Mind Me" on the second (two mellow, AC-friendly ballads), and "Lost in This Moment" (low-key, mainstream wedding song) on the third. The latter was even released as a single, quickly becoming a Black Sheep Hit.
 * Emilie Autumn: The Art Of Suicide and Shalott are this on Opheliac.
 * Britney Spears: In the break from dancing your ass off, purging your soul sense, she enjoys the ballad section of her tours so they do feature on her albums:
 * "Where Are You Now" on Oops, "Everytime" / "Shadow" during In The Zone, "Why Should I Be Sad" at the end of Blackout, "Unusual You" / "Out From Under / "Blur" / "My Baby" on Circus and "Trip To Your Heart" on Femme Fatale
 * The Pretty Reckless have this in the form of You on their debut album, about an unrequited crush.
 * The Foo Fighters have many. The very first was "Big Me" (which causes some Mood Whiplash on the album it's on), and then come "Walking After You", "Aurora", "Tired Of You", "Stranger Things Have Happened", the entire second disk of In Your Honor...
 * There's also Insane Clown Posse 's Miracles, which differs rather significantly from their normal fair.
 * While Lyriel is a Symphonic Metal band that tends towards the softer side of the genre, their album Paranoid Circus contains the track "Lullaby" which is exactly what the tittle suggests. This track is preceded and followed by tracks that feature aggressive drumming.
 * Blur give us "Tender" and "Sweet Song". And from Damon Albarn again, in Gorillaz we have El Manana from Demon Days (though the video is far from gentle) and Cloud of Unknowing in Plastic Beach (and again). On Melancholy Hill is fairly mellow and has very sweet lyrics, so it could fit, but is perhaps too upbeat for this.
 * Five Finger Death Punch has a few, especially with "Remember Everything". "Walk Away" and "Far From" are a couple more.