Sospiri. Adagio for String Orchestra Op. 70 with Harp (or piano) and Harmonium (or organ) ad libitum Full Score
Elgar's last work for String Orchestra started out as an intended companion piece for his Salut d'amour, but the composer realised he was writing something more substantial, so he changed the scoring and the name.
A set of orchestral parts to go with this score can be found at FMP 16062501