I don't get quite as passionate about the Double Concerto (for Oboe, Harp and Strings) as I do about say the 2nd or 3rd ("Tristan") piano concerti, but this music is undeniably glowing with inspired writing for the two Holligers, Heinz (Oboe) and Ursula (Harp), for whom it was written. It comes from the last year of the period of Henze's midlife lyricism (1963-6, before political interests disturbed the focus of his musical output. The recording here is very dated but the performance must be definitive, with both Holligers on sparkling form. As Elliott Carter observed in interview in 2001, Heinz Holliger's skill on his chosen instrument is "practically unlimited" - even thirty years later; this recording is just one of the higher and earlier peaks in an incredibly distinguished career.
I doubt many listeners will get so much out of the two string essays here. Henze's interest in writing for orchestral strings has continued right up until the recent tenth symphony, whose second movement draws on the experience of these two 1960's endeavours. But they are well crafted products, and as such give some answer to those critics of Henze who charge him with overloading his scores with too many extraneous aural curlicues.
Don't let that thought put you off in any way. The Double Concerto is a masterpiece and it alone is well worth your attention.