Philip Scowcroft has, I'm afraid, got some of his information mixed up (an easy thing to do with Holbrooke, as there is no definitive list of his works and Joe was always re-writing, re-scoring or renaming pieces and was also very cavalier about opus numbers). The Opus 61B Serenade is for ten wind instruments, harp and viola. The ten wind instruments are: oboe d'amore (or oboe); clarinet; basset horn (or cor anglais); soprano saxhorn (or cornet); baritone saxhorn (or cello) five saxophones - soprano, alto, tenor, baritone & bass. The saxhorn is sometimes confused with the flugelhorn but, while the saxhorn was invented in Paris by Adolphe Sax, the flugelhorn is of German origin and predates the saxhorn.
There is, as far as I am aware, no Serenade for five saxophones and seven woodwinds (though I am open to correction here) and I think Philip may have confused it with the Op. 61B piece in one of its many possible scorings. The Op. 99 sonata is simply the piano/saxophone score of the Op. 88 concerto which was originally written for performance on 3 saxophones, each of a different timbre: tenor, alto and soprano, as described by Philip. However, I know of no evidence to suggest that JH ever conceived of using five different saxophones. It is hard enough to find one player sufficiently proficient to play the virtuoso part on 3 saxophones of differing pitch, let alone five! And, indeed, JH later permitted the use of just alto and soprano in the concerto.
