It would be a misunderstanding to assume that a particular musical event is either marked or unmarked; rather, it may entail a number of oppositional relationships, each of which contributes something to the overall interpretation of the event. Thus, the minor mode in mm. 5-6 is both marked with respect to the previous major, and unmarked with respect to the following major. Furthermore, markedness values may actually reverse as styles grow or change. For example, the cadential 6/4 is marked as unstable relative to its syntactical role in a cadence. As an arrival 6/4, however, it may be marked as stable relative to its resolution of a German augmented-sixth (or other dissonant chord), especially when in conjunction with a strong thematic arrival. The pedal point on a dominant is marked as unstable in most environments, but it may be marked as stable when arising from an arrival 6/4. This historical style change, which might more neutrally be described as the contextual migration of a cadential 6/4, is ratified to rhetorical excess by Franz Liszt in what has been dubbed a "salvation 6/4." Richard Cohn (personal communication) brought my attention to a written account by Gustav Jenner of his composition lessons with Brahms (Frisch 1990: 185-204), in which Brahms cautioned against overuse of this kind of 6/4: "As excellent as the effect of this chord can be -- naturally I am referring only to cadential six-four chords -- it is often nothing but the symptom and in its flabbiness the true reflection of a completely lame and exhausted imagination" (198). The first movement of the F.A.E. Sonata for Violin and Piano, written by Schumann's student, Dietrich, provides ample illustration of the arrival 6/4's rhetorical abuse through overuse.
For an example of its noble/heroic usage in Beethoven, consider the second theme from the first movement of the last piano sonata, opus 111 (mm. 50ff.) Here, an arrival 6/4 (m. 50) links positive resolution of the thematized diminished-seventh chord (m. 49) with the initiation of a noble theme, and the nobility is cued by dotted rhythms. The theme would be unstable only to a Schenkerian; phenomenologically, it is exquisitely stable-- as though presented on a pedestal-- and only its brevity and parenthetical appearance between two appearances of a diminished seventh chord attest to its still-illusory status in the expressive drama of the movement. The tragedy of the first movement manages at best to hint at this more positive realm, ending with a Picardy third resolution at the end of the coda, where a somewhat resignational emphasis on the minor subdominant leads to a final resolution of the thematized diminished-seventh as viio7 to I. The unfinished character of this resolution leads us to expect a more profound transformation, which Beethoven provides with the transcendent, C major final movement.
The next three examples illustrate an interesting growth process with respect to the arrival 6/4 as a type in Beethoven's style, with extension to Schubert. In the coda to the finale of Beethoven's Sonata for Piano and Cello in A Major, opus 69, a subito piano marks a rhetorical arrival 6/4 on the subdominant in the piano (m. 195). Note, however, the pedal fifth of the IV chord is already present, and thus the pedestal effect is already in place in the piano part. Instead of the lowered third (F-natural) which would occur with the German augmented-sixth (not appropriate as an elaboration of the subdominant), Beethoven resolves an augmented dominant of IV, written with a raised second (E#). Note also that the cello has the bass, emphasizing the resolution of E# to F#, and producing in effect an arrival 6/3 on the subdominant.
In Beethoven's Sonata for Piano and Cello in D Major, opus 102, nº2, the coda to the first movement features the arrival 6/3 on the tonic chord (m. 143), logically appearing in this inversion because of its proper voice-leading resolution of an inverted German augmented-sixth chord (m. 142) with the lowered-3 in the bass. The sense of a "breakthrough" as arrival (or return, in this case) is perhaps even stronger because of the unusual inversion. Clearly, Beethoven is expanding his use of this effect, and the arrival 6/3 is an example of style growth of a type.