Most achingly-beautiful music

My three choices are Ravel's String Quartet in F major by the Ad Libitum Quartet,Bela Bartok String Quartet No. 4 by the Juilliard String Quartet, and Shostakovich String Quartet No. 8 in C minor by the Emerson String Quartet.
One thing I have just learned about classical music is that one piece played by different musicians can affect you differently.The musicians that I named seem to play the pieces that I named just a bit more effectively than some others that I have heard.

1) Liszt - Benediction de Dieu dans la solitude. Favorite recording by Garrick Ohlsson on EMI/Angel, unfortunately OOP.

2) Durufle - Requiem. Robert Shaw, Telarc

3) Mozart - Ave Verum Corpus. Robert Shaw (again.) This should have been the closing theme for Amadeus...

4) Okay, so I cheated. Morten Lauridsen - Lux Aeterna. Paul Salamunovich with the Los Angeles Master Chorale. Proving (once again) Maestro Salamunovich to be the finest choral director ever to have graced our planet...

If these don't move you, you have no soul.

Verdi's Requiem - the whole thing.

Rodrigo's "Concierto de Aranjuez" is simply The most haunting and beautiful melody I have ever heard...

Bach's "Air For the G String"

For popular music... any ballad played by the late cornetist Bobby Hackett (who can be heard on most Jackie Gleason recordings, "Music For Lovers Only", etc.)

The 2nd movement of Rodrigo's "Aranjuez" is the specific melody I had in mind. But I will shamelessly use this opportunity to mention another hauntingly beautiful melody: Massenet's "Meditation" from Thais...