Glad to find so many other fans of Soave Il Vento from Cosi Fan Tutte! That's my funeral music.
When I am Laid in Earth, from Dido and Aeneas by Purcell. (This is very, very sad but one of the most beautiful pieces of music ever written.)
Anything by Bach. I also love Shostakovich and I find his 24 Preludes and Fugues, which is based on Bach, very calming.
Satie's piano music (Gymnopedies) is also lovely.
Rhapsody in Blue, George Gershwin. (Also Summertime from Porgy and Bess.)
The Trout Quintet by Schubert.
Finlandia, Sibelius.
Ma Vlast, Smetana.
Khachaturian: Adagio from Spartacus - much better known to British people of a certain age as the Onedin Line theme.
Prokofiev's Peter and the Wolf, Lieutenant Kije suite and Classical Symphony.
Carmen by Bizet.
Collection of the really good bits from Verdi and Puccini operas, e.g. Nessun Dorma, Chorus of the Hebrew Slaves.
The Nutcracker Suite, by Tchaikovsky.
Rachmaninov 2nd Piano Concerto.
Peter Grimes, Benjamin Britten. I find this desperately sad as well as beautiful.
We have a collection of English folk songs by Percy Grainger. Varied moods, but all tremendously hummable.