Which classical music would you recommend for ASMR like effects?

Not having gone there, I can recommend some classical pieces for serenity, for an ethereal experience, and so on. Many Mozart and other arias just transform the moment.

Some favs: Casta Diva, Bellini. Ruh Sanft, Mozart. Dove Sono, Mozart. Sull 'Aria, Mozart (Shawshank "fame") Porgi Amor, Mozart (see a pattern here?)

Brahms: Third movement Piano Concerto #2

Beethoven: slow movement Archduke Trio 3rd movement - Andante Cantabile

Many late Beethoven string quartets, and last piano sonata.

(Beethoven was deaf around and after his third symphony, so he composed without hearing aurally)

Beethoven Piano Concerto 1, second movement

Beethoven Piano Concerto 2, second movement

Chopin Ballade slow movement

Chopin Sonata Op 58. slow movement

Richard Strauss: final trio from Der Rosenkavalier

Just off the top. I am a piano and opera freak.

MANY MORE

Singers and other instrumentalists are welcome to add.