The bass register is something like this (played with a ritardando):
And here's the beginning of Bach's toccata:
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In both, there's a diatonic descent followed by an accidental on the seventh degree of the scale (G# in the A minor of "Indication" and C# in the D minor of Bach's toccata). This accidental is also at or near the end of the phrase and played with a longer note value than the preceding notes.
There's a definite similarity here, and Rod Argent sometimes mentions Bach (in the liner notes for Classically Speaking, he wrote, "And I've always loved Bach!" and in a 2009 BBC radio segment, he called Bach "without any question, the greatest musician who ever lived"), but of course, it's just speculation on my part that this is an instance of Bach's influence.
For what it's worth: in the live version of "Hold Your Head Up" from the Zombies' concert at Abbey Road, Argent even plays part of the fugue that follows this toccata.
