Two main kinds of transformations were applied to the primary thematic materials in The Angel of Death: conceptual transformations notated in the instrumental writing, and computer processing of the recorded thematic materials. The Composition Stream described the issues involved in conceiving the materials for two instrumentations, one with a single musician and another with 16 musicians and a conductor. It also described the way a given set of materials is altered across the two parts of the piece. The Perception Stream studied how timbre is encoded in a listener's memory for materials from The Angel of Death and also from a symphonic poem by Liszt. Timbre would seem to be an integral part of this memory code, being intimately bound up with pitch and rhythm processing. Recognition of a thematic subsection is less good when the instrumentation changes than when it stays the same, for both musician and nonmusician listeners. While this result underlines the essential form-bearing role of timbre, particularly in contemporary music, it also suggests that musical variation involving timbre may pose interesting challenges for listeners.
Another kind of transformation applied through instrumental writing occurs in the derived regions of The Angel of Death — Transitions and Combinations. The Composition Stream laid out the conception of these two kinds of musical development in terms of long trajectories that move from a predominance of one material to that of another for the Transition ideal, and of an interwoven mosaic structure of highly characterized and distinctive excerpts from two or three themes for the Combination ideal. The Analysis Stream examined these kinds of transformations within the larger structure of the work, in particular its two versions: Sectional-Domain vs. Domain-Sectional. The notion of a reversal structure was developed: however it first occurs, material returns in the second part having been transformed and renewed (in addition to being accompanied by the computer component which further skews the perspective). Such renewal can be realized either by the "transformed" writing in D or by means of the original materials in S, depending on the version played. Whether or not this structural symmetry is actually perceived will be dealt with in all three streams in the next section. Several kinds of variation in the instrumental writing were developed in the Analysis Stream: variation by making the material more heterogeneous (D vs. S), by continuous transformation (Transition, Combination regions), and by derivation (RepStrat, Interlude and Epilog regions). Many of these represent new transformation techniques not typical of Reynolds previous work and are thus new directions in his compositional evolution.
Characteristic of many of Reynolds' pieces is the presence of computer-processed transformations of recorded thematic materials drawn from the score. The Angel of Death draws from many kinds of processing that Reynolds has used in the past, including analysis/resynthesis, filtering, editorial (cutup) algorithms and spatialization, but adds many new uses of these techniques for specific aesthetic goals. In particular, the transformational approaches to the computer "images", as outlined in the Composition Stream, are of two main kinds, in keeping with the many levels of dichotomy present in the piece (piano vs. orchestra, S vs. D, S-D vs. D-S, and so on). The computer images were conceived as deriving from the S and D ideals: D-like images are organic and broadly sculpted, generally arising out of a singular, basic process, whereas S-like images are mosaic in nature, employing an array of processing strategies and techniques, and having a distinctive temporal design. The Analysis Stream discussed the central role that the computer component plays as a key persona in the dramatics of the work. It is perceptually distinct from the instrumental parts, although it is made up of materials derived from those parts. Within the Perception Stream, one issue related to the computer transformations was the degree to which exposure to original thematic materials might facilitate memory coding or refresh the memory trace when transformations of those materials occur by way of Reynolds' editorial algorithms SPLITZ and SPIRLZ. Only minor facilitating effects on recognition for one kind of transformation algorithm were demonstrated; they occurred in only one experiment when a previously heard transformation of the SPIRLZ type was refreshed in memory by original materials. One should be careful, however, not to confuse perceived similarity or even absolute recognition of materials heard previously with these explicit memory facilitation effects. The possibility of implicit interactions between memory traces of original and transformed materials — they can be heard in either S-D or D-S order, and the full themes are sometimes preceded by derived materials — cannot be ruled out. And they certainly may also evolve with more extended familiarization through listening to the musical universe of this piece and to the composer's work in general.
From this point, the Composition Stream will relate how various aspects of the composition were reconsidered subsequent to the writing of the Sectional part and then how the Domain part with its formal parallels to the Sectional part was elaborated. The Perception Stream will describe the continuous-response experiments performed in a concert situation at the European and North American premiers of The Angel of Death and discusses a dynamic conception of musical form. The Analysis Stream will also explore this dynamic conception of form from both analytic and perceptual angles.