A "Toccata" is a piece with lots of motion, normally executed by one performer. The prefix «Deep» may here indicate several layers of motion, different tasks being performed at different speeds. Together they form a «sea of sound» where fast and slow time are working in parallel.
From the start of the piece we can hear the organ diving down into the orchestra, transmitting motion and energy and then becoming immersed in the resulting sound web. This basic gesture recurs again and again, interpreted in different ways, in a variation form.
Apart from the improvisation-like detail work, the construction of the piece follows a simple architectural plan. Comparable to the paintings of Escher, with endless staircases, there is a harmonic structure moving slowly downwards at a constant speed through all the piece. Against this, there is a counterpoint of ascending lines that becomes more and more prominent as we approach the end.
There are many other sources of inspiration: the film «Inception» with its architecture that is mirrored upwards, where you finally are not sure what is up and down. Also, Gustave Doré’s exuberant illustrations to «Paradise Lost» have been in my mind.