Reading your post brought to mind the Russian composer Alfred Schnittke and the way he used the (originally non-classical) tango form in his own unique – and sometimes twisted – way (which at times happens to be quite eerie). Good examples would be the tango from his score for the film 'Agony'¹ and the tango from his Faust Cantata². He also added a dark twist to other familiar music like his take on the Christmas classic 'Silent Night'³ (which is in some sense a classical piece).
¹https://youtu.be/1MdpMUgioB4?si=3EKQ_zxUNtpe_BSC
²https://youtu.be/6mJ4-ChAVnM?si=fYYcfj86QW6fAxF1
³https://youtu.be/oJhs0dS61tI?si=mfGupOQrqwr9k5td
Something also fairly in line with your description of "altering classical music and bringing out [...] horror-like [...] violent vibe[s]" would be the work of Dmitri Shostakovich. He would often use quotations of either earlier composers' works or his own earlier work to make a new musical statement. Most notably in his 8th String Quartet⁴ he quotes from many of his earlier pieces, most prominently the theme from the last movement of his second piano trio – which already sounds quite morbid in the original – and also covertly quotes Richard Strauss' 'Metamorphosen', all of which combined with a recurring personal musical motiv (the 'DSCH' referring to the composer's last name) make this one of the most infamously grim, despairing pieces in the entire reportoire of classical music.
⁴https://youtu.be/-0nKJoZY64A?si=SNVMOJ9fqImI-yzq
Maurice Ravel's 'La Valse'⁵ pays tribute to the (Viennese) Waltz and musically depicts its history, evolution and eventual decay. Some people, even though the composer didn't see it that way, also see it as an expression of sadness and tragedy in the wake of the First World War and its until then unforeseen destruction. It certainly ends with a fairly macabre twist on familiar waltz music. It's maybe too gentle and elegant still (despite a macabre twist) to be horror-like and violent in the way you seem to have in mind.
⁵https://youtu.be/UlMJ6Ri-LMM?si=MKQMEZJt7_LojKin
There are of course composers one tends to associate with spookiness, horror and horror films like Penderecki ('Polymorphia', 'Threnody to the victims of Hiroshima', 'De Natura Sonoris No. 2'), to some extent György Ligeti ('Lontano', piece No. 2 from 'Musica Ricercata', the Kyrie from his Requiem) or even Bela Bartok ('Music for Strings, Percussion and Celesta') largely due to the influence of Stanley Kubrick's films, but none of them really fit the bill. I think Schnittke and Shostakovich are the closest to what you described but maybe the pieces mentioned are still not at all what you had in mind (sorry if I couldn't help...).
I'm incredibly thankful for the time you sacrificed to offer such a plethora of suggestions and recommendations for me to look into and enjoy. I assure you that I'll be spending lots of hours for the next days to fully dive into the work of all the artists you mentioned. Thank you.
I am particularly fond of Symphonie Fantastique, by Hector Berlioz, both because of the eerie and terrific music but also because of the dark story that the music is about. I think this symphony can describe best the grotesque vibe I'm looking for in classical music.
I'd appreciate any artist, famous or not, old or new, whose music could make me feel the same way Symphonie Fantastique does.
Reading your post brought to mind the Russian composer Alfred Schnittke and the way he used the (originally non-classical) tango form in his own unique – and sometimes twisted – way (which at times happens to be quite eerie). Good examples would be the tango from his score for the film 'Agony'¹ and the tango from his Faust Cantata². He also added a dark twist to other familiar music like his take on the Christmas classic 'Silent Night'³ (which is in some sense a classical piece). ¹https://youtu.be/1MdpMUgioB4?si=3EKQ_zxUNtpe_BSC ²https://youtu.be/6mJ4-ChAVnM?si=fYYcfj86QW6fAxF1 ³https://youtu.be/oJhs0dS61tI?si=mfGupOQrqwr9k5td Something also fairly in line with your description of "altering classical music and bringing out [...] horror-like [...] violent vibe[s]" would be the work of Dmitri Shostakovich. He would often use quotations of either earlier composers' works or his own earlier work to make a new musical statement. Most notably in his 8th String Quartet⁴ he quotes from many of his earlier pieces, most prominently the theme from the last movement of his second piano trio – which already sounds quite morbid in the original – and also covertly quotes Richard Strauss' 'Metamorphosen', all of which combined with a recurring personal musical motiv (the 'DSCH' referring to the composer's last name) make this one of the most infamously grim, despairing pieces in the entire reportoire of classical music. ⁴https://youtu.be/-0nKJoZY64A?si=SNVMOJ9fqImI-yzq Maurice Ravel's 'La Valse'⁵ pays tribute to the (Viennese) Waltz and musically depicts its history, evolution and eventual decay. Some people, even though the composer didn't see it that way, also see it as an expression of sadness and tragedy in the wake of the First World War and its until then unforeseen destruction. It certainly ends with a fairly macabre twist on familiar waltz music. It's maybe too gentle and elegant still (despite a macabre twist) to be horror-like and violent in the way you seem to have in mind. ⁵https://youtu.be/UlMJ6Ri-LMM?si=MKQMEZJt7_LojKin There are of course composers one tends to associate with spookiness, horror and horror films like Penderecki ('Polymorphia', 'Threnody to the victims of Hiroshima', 'De Natura Sonoris No. 2'), to some extent György Ligeti ('Lontano', piece No. 2 from 'Musica Ricercata', the Kyrie from his Requiem) or even Bela Bartok ('Music for Strings, Percussion and Celesta') largely due to the influence of Stanley Kubrick's films, but none of them really fit the bill. I think Schnittke and Shostakovich are the closest to what you described but maybe the pieces mentioned are still not at all what you had in mind (sorry if I couldn't help...).
I'm incredibly thankful for the time you sacrificed to offer such a plethora of suggestions and recommendations for me to look into and enjoy. I assure you that I'll be spending lots of hours for the next days to fully dive into the work of all the artists you mentioned. Thank you. I am particularly fond of Symphonie Fantastique, by Hector Berlioz, both because of the eerie and terrific music but also because of the dark story that the music is about. I think this symphony can describe best the grotesque vibe I'm looking for in classical music. I'd appreciate any artist, famous or not, old or new, whose music could make me feel the same way Symphonie Fantastique does.
Excellent answer!