Nineteenth-century forms challenge Sonata Theory’s hierarchical distinction between sonata form and the “parageneric” space outside it (introduction, coda and developmental interruptions). This issue is exemplified in Hepokoski’s “introduction-coda frame” deformation (1993): if an expanded parageneric exterior overshadows the interior sonata, then the traditional hierarchy is reversed. Moving beyond straightforward hierarchical inversion, the introduction-coda frame can involve more liminal situations as parageneric material is interpolated into the sonata form. These interpolations challenge the relationship between sonata and non-sonata space, conjuring deformational imagery of normative bodies being distorted (Straus 2006). Building on this intersection with disability studies, Quaglia (2015) describes parageneric space as a “musical prosthesis” attached to the sonata that compensates for its formal inadequacies. This relationship between the sonata body and its prosthetic attachment is challenged by the introduction-coda frame’s liminal interplay between sonata and parageneric spaces, compelling a more metaphorically precise framework.

Extending Quaglia’s prosthetic account of parageneric space, this presentation develops a new typology of the introduction-coda frame, adapting Cone’s (1962) terms of “stratification,” “interlock” and “synthesis.” I critique Hepokoski and Darcy’s hierarchical account by exploring parageneric space’s etymology and problematizing the term’s grounding in narrative theory. To provide an alternative foundation, I draw on Mitchell and Snyder’s (2000) concept of “narrative prosthesis” and Caplin’s (1998) form-functional theory. These frameworks recontextualize accounts by Quaglia (2015) and Horton (2021), where development interpolations maintain their parageneric identity or change formal function over time. A form-functional approach to parageneric intrusions reveals more complex interactions between different formal layers, which I explore through the case studies of Mozart’s String Quartet No. 11, Schubert’s Unfinished Symphony and Tchaikovsky’s First Symphony. Stratification maintains a distinction between two different levels but grants them equal importance within a larger formal narrative. Interpolations within sonata space lead to interlock between these layers. Taken to the extreme, synthesis omits the sonata-parageneric division entirely. The introduction-coda frame’s inside-outside dynamics facilitate the rethinking of Hepokoski’s other deformations in terms of sonata-parageneric interactions that critically transform traditional formal conceptions. Beyond formal theory, theorizing parageneric space’s prosthetic dimension also expands music theory’s capacity for interdisciplinary discourse with disability studies.

Kurt Westphal (1907–1978) remains virtually unknown to English-speaking music theorists despite James Webster’s brief invocation of his Form/Formung distinction in Musical Form, Forms, and Formenlehre (2009). His major theoretical work, Der Begriff der musikalischen Form in der Wiener Klassik (1935), has never been translated. This paper introduces Westphal’s Formenlehre to English-speaking scholars, contending that his concept of the Verlaufskurve (progression curve) offers an alternative to the bottom-up, additive models derived from Riemann, positing that form resides not in the composition’s score but in the listener’s perception of its development. It rests on the Formungsgrundlagen (the foundational forming forces of rhythm, tonality, dynamics, and metric accentuation) which constitute the necessary but insufficient conditions for large-scale coherence.

Drawing on Gestalt psychology—particularly von Ehrenfels and the musical applications of Ernst Kurth—Westphal develops a holistic approach centered on the Verlaufskurve, which he defines as “the force that uniformly permeates the parts of a work or movement” and “the true creator of wholeness in any large form.” The curve exists not as objective architecture in the score but as psychological reality emerging in the listener's real-time engagement with music. For Westphal, the familiar schema of first theme, transition, second theme, and development is formally empty. A movement’s formal identity lies in the curve that animates it from within.

Westphal’s theory emphasizes the whole’s primacy over its parts. A part’s function is defined not just by its internal structure, but also by the influences originating from the whole, including its connections to adjacent parts and its role in the overall development. The same material can thus assume different formal functions at different points in the curve. This provides analytical vocabulary for phenomena we hear but struggle to describe systematically—what Webster calls the “processual” dimensions of form: momentum, tension distribution, psychological weight.

Recovering Westphal’s ideas addresses a persistent methodological blind spot: our inherited tools privilege score-based, objectifiable features over experiential ones. Westphal’s work suggests that asking “how do parts combine into wholes?” may be less productive than asking “how do wholes manifest through parts?”

A primary characteristic of sonata-form movements is the recapitulation of themes from the exposition. A handful of exceptional works feature recapitulations that substitute entirely new material. To accommodate them, I propose “non-congruent” sonata form, whereby two seemingly independent sonata-form halves are sutured together at the midway point. Such assemblages, in my view, yield successful sonata forms, because each component exhibits the characteristics requisite for its formal function.

How can a recapitulation function as such when it does not recall earlier material? Two dominant analytical approaches differ in their answer. Dialogic theory (e.g., Hepokoski and Darcy) prioritizes the origin of a given theme; a sonata that “recapitulated” new material would be considered deformational, if a sonata at all. By contrast, form-functional theory (e.g., William Caplin) prioritizes internal makeup and treats thematic origin as ancillary. Main themes are tight-knit; subordinate themes engage in harmonic and formal loosening, defer articulation of their goal PAC, and, in the recapitulation, sound in the home key. Tightening and loosening express thematic function in the absence of motivic reworking.

In non-congruent sonata form, a hole appears in the middle of the movement where the material shifts from first half to second half. Two options for non-congruence appear in the 18th- and 19th-century repertoire respectively. (1) “Sectional” non-congruent form places the point of non-congruence between the two reprises. In Scarlatti's Sonata in C Major, K. 170, the second reprise features a new tempo and time signature. (2) “Transformative” non-congruent form places the point of non-congruence within the development. This strategy, associated with the absence of repeat signs, transforms ongoing material, reflecting a Romantic ideal of progressive reinterpretation. The Finale of Schumann's Symphony No. 2 provides an exemplar.

Because these movements’ endings do not recapitulate earlier material, they have not consistently been viewed as sonata forms. Closer inspection of their form-functional construction reveals recapitulations identifiable through tonal and phrase-structural features. Non-congruent sonata form expands our understanding of how formal function is expressed.