The whole piece is a rounded binary (A)Exposition (00:12) - The exposition is constructed as a period. The antecedent phrase is really simple, it's a 4 measure antecedent but instead of ending with a half cadence, it's replaced by a Dominant Arrival (00:26) in measure 5. In measure 6, Mendelssohn restated the basic idea, but the contrasting idea is expanded by 2 measures. At the start of consequent, we might think that this chord is a dominant of the vi chord in the home key with a submediant pedal, which it actually is, but Mendelssohn used the vi chord from the preceding measure as a pivot chord to the subordinate key (V: Bb major), so the dominant chord and the pedal is actually a Dominant of supertonic above a supertonic pedal, it is an emphasis of predominant function. After the expansion, we get a Dominant 64-73 chord, which is then resolved to I. The consequent modulated to the subordinate key, confirmed by the PAC. I still consider this as a period because even though the final dominant of the antecedent phrase didn't end with a half cadence, the restatement of the basic idea after the dominant 7th tells us that the phrase is a consequent. Well, this may be a hybrid theme, a Compound Basic Idea + Consequent, but I know that most hybrid themes of this kind, the Compound Basic Idea doesn't end with a root position Dominant 7th. (B) Contrasting Middle (01:34) - The Contrasting Middle is very sentential in design. This section achieved its contrast by changing the modality, since the exposition modulated to the subordinated key, it is understandable that this section, instead of emphasizing the dominant further, goes back the the home key but in minor. The first 4 measure is a presentation phrase, m. (14 - 15) is the basic idea, these two measure has almost same melodic-motivic content but measure 15 is not a repetition or response to the preceding measure since it has a different harmonic support, it even modulates to the subordinate key, relative major (Gb major), but it quickly returned to the home for the repetition of the basic idea. After the repetition, we get a one measure idea which resembles the basic idea, this one measure idea is being supported by a dominant chord in subordinate key (Gb major) sustained from the end of the basic idea of the presentation phrase, the 64 being a neighbor chord. This one measure idea is then repeated (01:52), just like how most continuation ideas, but the 64 chord didn't resolve to the dominant 7th but progressed to vii7 (01:53) of vi, this vi chord, although it is a resolution of dominant from the preceding measure, I don't think it is part of it. The vi chord is a pivot chord, a tonic chord in the home key minor. The idea is still part of the continuation phrase, and it is also supported by single harmony, the iv chord is just a neighbor chord, but instead of using the 64 technique, the bass actually changed, and the one measure idea is actually a bit shorter than the idea from the earlier part of the continuation, and it is also repeated. After the repetition, the idea is once again fragmented (02:00) but this time the iv chord isn't a neighbor for the tonic chord but as an initial subdominant for the cadential progression, because in the 3rd beat (02:06 of measure 23, we get a Dominant arrival, and the end of the contrasting middle. This section is loose, and a bit unconventional. (A') Recapitulation (02:09) - In the recapitulation, the exposition is restated, the antecedent is not that different from the one in the exposition. After the antecedent, we are definitely expecting the consequent phrase, but Mendelssohn replaced the consequent with a continuation, so now the recapitulation is not a period but an actual hybrid theme, an Antecedent + Continuation. In this continuation phrase, the one measure idea from the continuation phrase of contrasting middle is used, with the same characteristics, like the first statement is supported by I-V7 but the next measure is supported by I-vii7/vi, after this continuation phrase we get our cadential phrase, also resembles the idea from contrasting middle (01:55), the idea is "repeated" down a third, we then get a PAC. The contrasting middle and recapitulation is then repeated, since the piece is a rounded binary. Now, after the repetition of B and A', Mendelssohn could have finished the piece, but the dominant 7th from measure 30 (03:37) resolved to V7/IV instead of tonic; a Deceptive Cadence. The accompanimental figuration resembles the retransition from the exposition. The V7/IV is extended, in measure 34 the chord is finally resolved to IV but with a Tonic Pedal below, the reason why I considered this as a pedal and not a IV64 is that the next measure is vii7, also above a tonic pedal, this vii7 resolved to I chord, but not a PAC but a restatement of the basic idea again, an evaded cadence. This restatement of idea is not surprising in this case, if you noticed, at the start of the recapitulation, the basic idea has a dominant pedal below, and this dominant pedal weakened the tonic, to compensate for the tonic weakening, Mendelssohn restated this the basic idea with the right bass, it would be redundant to restate the whole theme so after the basic idea, we get an ascending notes of dominant 7th and finally resolved to I.
The whole piece is a rounded binary
(A)Exposition (00:12) - The exposition is constructed as a period.
The antecedent phrase is really simple, it's a 4 measure antecedent but instead of ending with a half cadence, it's replaced by a Dominant Arrival (00:26) in measure 5. In measure 6, Mendelssohn restated the basic idea, but the contrasting idea is expanded by 2 measures. At the start of consequent, we might think that this chord is a dominant of the vi chord in the home key with a submediant pedal, which it actually is, but Mendelssohn used the vi chord from the preceding measure as a pivot chord to the subordinate key (V: Bb major), so the dominant chord and the pedal is actually a Dominant of supertonic above a supertonic pedal, it is an emphasis of predominant function. After the expansion, we get a Dominant 64-73 chord, which is then resolved to I. The consequent modulated to the subordinate key, confirmed by the PAC.
I still consider this as a period because even though the final dominant of the antecedent phrase didn't end with a half cadence, the restatement of the basic idea after the dominant 7th tells us that the phrase is a consequent. Well, this may be a hybrid theme, a Compound Basic Idea + Consequent, but I know that most hybrid themes of this kind, the Compound Basic Idea doesn't end with a root position Dominant 7th.
(B) Contrasting Middle (01:34) - The Contrasting Middle is very sentential in design. This section achieved its contrast by changing the modality, since the exposition modulated to the subordinated key, it is understandable that this section, instead of emphasizing the dominant further, goes back the the home key but in minor. The first 4 measure is a presentation phrase, m. (14 - 15) is the basic idea, these two measure has almost same melodic-motivic content but measure 15 is not a repetition or response to the preceding measure since it has a different harmonic support, it even modulates to the subordinate key, relative major (Gb major), but it quickly returned to the home for the repetition of the basic idea. After the repetition, we get a one measure idea which resembles the basic idea, this one measure idea is being supported by a dominant chord in subordinate key (Gb major) sustained from the end of the basic idea of the presentation phrase, the 64 being a neighbor chord. This one measure idea is then repeated (01:52), just like how most continuation ideas, but the 64 chord didn't resolve to the dominant 7th but progressed to vii7 (01:53) of vi, this vi chord, although it is a resolution of dominant from the preceding measure, I don't think it is part of it. The vi chord is a pivot chord, a tonic chord in the home key minor. The idea is still part of the continuation phrase, and it is also supported by single harmony, the iv chord is just a neighbor chord, but instead of using the 64 technique, the bass actually changed, and the one measure idea is actually a bit shorter than the idea from the earlier part of the continuation, and it is also repeated. After the repetition, the idea is once again fragmented (02:00) but this time the iv chord isn't a neighbor for the tonic chord but as an initial subdominant for the cadential progression, because in the 3rd beat (02:06 of measure 23, we get a Dominant arrival, and the end of the contrasting middle.
This section is loose, and a bit unconventional.
(A') Recapitulation (02:09) - In the recapitulation, the exposition is restated, the antecedent is not that different from the one in the exposition. After the antecedent, we are definitely expecting the consequent phrase, but Mendelssohn replaced the consequent with a continuation, so now the recapitulation is not a period but an actual hybrid theme, an Antecedent + Continuation. In this continuation phrase, the one measure idea from the continuation phrase of contrasting middle is used, with the same characteristics, like the first statement is supported by I-V7 but the next measure is supported by I-vii7/vi, after this continuation phrase we get our cadential phrase, also resembles the idea from contrasting middle (01:55), the idea is "repeated" down a third, we then get a PAC. The contrasting middle and recapitulation is then repeated, since the piece is a rounded binary. Now, after the repetition of B and A', Mendelssohn could have finished the piece, but the dominant 7th from measure 30 (03:37) resolved to V7/IV instead of tonic; a Deceptive Cadence. The accompanimental figuration resembles the retransition from the exposition. The V7/IV is extended, in measure 34 the chord is finally resolved to IV but with a Tonic Pedal below, the reason why I considered this as a pedal and not a IV64 is that the next measure is vii7, also above a tonic pedal, this vii7 resolved to I chord, but not a PAC but a restatement of the basic idea again, an evaded cadence. This restatement of idea is not surprising in this case, if you noticed, at the start of the recapitulation, the basic idea has a dominant pedal below, and this dominant pedal weakened the tonic, to compensate for the tonic weakening, Mendelssohn restated this the basic idea with the right bass, it would be redundant to restate the whole theme so after the basic idea, we get an ascending notes of dominant 7th and finally resolved to I.
Ediwao daryl