Murray Gold composed the theme music for the 2005 Series, using elements
from the original Delia Derbyshire version, with a few modern instrumental sounds and fast-pacing harmonics thrown in.
However, Gold decided to remove the 'Middle Eight' from the 2005 version, as it reminded him
of 'Feed The World'. Some fans were angry by this, but all was not lost.
For the 2005 Xmas Special 'The Christmas Invasion', Murray Gold composed a revised version
of the 2005 Opening Music (which only saw use in 'The Christmas Invasion'), where some very minor changes were made. But the
Closing Theme Music was changed completely. Gold opted for a more orchestral, more traditional sound to the Doctor Who theme.
Bringing joy to my ears, the Middle Eight was finally ignited as well.
The 'new' 2006 theme music was only created for the closing credits though. The original Murray
Gold version, from the 2005 Series, remained in place for the opening title sequence of the 2006 Series - but the new version
stayed in place for the closing credits.
One exception was the closing credits for 'Rise Of The Cybermen', as the closing theme started
off with the 2005 version, and then blended with the 2006 version, about half way through (just at the point
where the 'middle eight' begins) - this version is also downloadable below.