One of Howells' lesser known works, this the first of the Two Slow Airs (written in 1928) was originally scored for Violin and Piano and was intended to be an exam piece for the ABRSM Violin Intermediate grade. Whilst not the original version, I find this organ arrangement to be rather effective.
Arrangement: Robin Wells
The first solo voice (starting at 0:40 ish) is the Choir Clarinet 8' with the Lieblich Gedact 8' (accompanied by the Swell strings).
The second (starting at 2:20 ish) is the Swell Oboe 8' with the Flauto Traverso 8' (accompanied by the Choir and Echo strings, including the unusual Cello und Violone 8')