In commemoration of the 50th anniversary of the death of Edgard Varésè, residual drift is derived from a sonogram of his percussion work Ionisation (1931). Apart from alluding to the origin of the piece from the residue of a Varésè work, the title uses terms from particle physics which perhaps bear the same "fantastic" qualities in our own time that the term ionisation did in 1931. he sonogram was used as the basis for a score for amplified bass flute and was resonified to create an electronic component. Both the score and the electronics can be played via the Decibel Scoreplayer. To create the the electronic component each pixel of the sonogram was rendered as a sine tone, with frequency and amplitude determined by vertical height and shade respectively. The graphical score was rendered in broadly three hues corresponding to varied tonal qualities of the bass flute. The method of rendering these qualities is determined by the performer. The work can theoretically be performed simultaneously with Ionisation. The work is dedicated to Cat Hope.