Pluto, Paradoxically, Joins ‘The Planets’

To complete Holst's series, Colin Matthews wrote Pluto.  The movement premiered in 2000.  Coincidentally, Pluto's status as a planet was in question at the time. 

Q&A: Mike Brown: Eight Is Enough

For more information about the dethroning of Pluto, read this interview with Mike Brown who wrote  the book How I Killed Pluto and Why It Had It Coming.