The theme often appears with its entrance varied. In m. 11, the lower voice presents a portion of the theme starting half a beat early, on the downbeat of beat 1.

Score example provided by:  Bärenreiter Verlag

Sinfonia No. 10 in G Major

This Sinfonia conveys Bach's cheerful disposition. A characteristic feature of this Sinfonia is that the first note of the subject enters on an off-beat and is sustained for the longest duration. Given the basso continuo-like bass movement, the piece should be performed with vitality, which implies a relatively fast tempo.

Another characteristic of this Sinfonia is that the rhythm of the subject transforms depending on the context. In such cases, since it differs from the original subject, one might argue that it should not be considered the subject. Alternatively, it could clearly be judged as the subject. This is left to the performer's discretion.

Let us now examine the opening. In the soprano voice at measure 1, the phrase entering on the off-beat of beat 1 is the subject. This subject concludes on B on the downbeat of beat 1 in measure 3. We will define the subject as extending up to this point. The second subject appears in the alto voice, entering on the off-beat of measure 3. It begins on D and ends on F-sharp on beat 1 of measure 5.

Now, I would like to draw your attention to the soprano voice entering on beat 1 of measure 5. It bears a strong resemblance to the subject. The two differences are that it does not enter on an off-beat and its final note descends. A further issue arises: the bass voice entering on the off-beat of beat 1 in measure 7 clearly resembles the subject, but it lacks the final note. Previously, the final note would either descend or ascend by a second, but that note is absent here. Instead, a clear sequence begins.

Considering this, it might simplify matters to define the subject as beginning from the off-beat soprano in measure 1 and extending to the final A in measure 2. However, when contemplating the subject itself, ending on A feels rather unsettling; one strongly desires this note to resolve to B or G. The question is how to interpret this.

Moving on, the alto voice starting on E on beat 2 of measure 12 also closely resembles the subject, but its rhythm is different. The soprano voice starting on A on beat 2 of measure 13 is exactly the same. And perhaps from beat 2 of measure 15, the soprano voice beginning around this point is also remarkably similar to the subject. Furthermore, a subject-like voice emerges from B in the alto on beat 1 of measure 20. The bass parts in measures 22 and 24 also resemble the subject. Additionally, from G in the alto on beat 2 of measure 26, after a sequence spanning measures 27-30, it leads to the soprano on beat 2 of measure 31.

Given this, it appears that only the first two instances truly begin with a dotted eighth note on an off-beat and conclude by ascending a second. How to interpret these facts and incorporate them into performance is left to the performer. For instance, while the E in the alto emerging from beat 2 of measure 11 could be considered a rhythmic transformation of the subject, it would feel very unnatural to play the G-A-G-F# on beat 1 softly (p) and then suddenly introduce the designated thematic voice loudly from beat 2.

Instead, regarding the G-A-G-F# on beat 1, I feel it would flow more naturally to consider the initial G as the final note of the previous measure and perform the subsequent A as the start of the subject. What are your thoughts?

Finally, I will note the peak points and the quietest sections as I perceive them. The peak of this Sinfonia is in the soprano at measure 16, where the tension is highest. Next, beat 1 of measure 22 is the quietest section, and then the soprano at measure 27 presents a section with tension as high as, or even higher than, measure 16. For your reference.