Gustav Holst was an English composer of the same era as Elgar, but, like Pachelbel, is really only famous for one piece, his Planets’ Suite. This is a series of seven "movements", one for each of the non-Earth planets known in Holst’s day (i.e., all of the planets but Earth and Pluto).

The basic inspiration for the characterisation of the planets is their astrological nature, not necessarily the Graeco-Roman gods. For example, Neptune is Neptune, the Mystic, nothing to do with Neptune/Poseidon, god of the sea.
One of the themes to Jupiter was subsequently used as the basis for rather a patriotic hymn (I vow to thee my country), in much the same way as one of Elgar’s Pomp and Circumstance marches was turned into Land of Hope and Glory.

On Wikipedia :  Gustav Holst

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