An interesting parallel has been made by J. B. Hutchings in his “The Baroque Concerto” (London 1961), between the Bolognese masters, who established the concerto-form, and the Orchestra of Mannheim in the second half of the XVIII century, who gave a crucial contribution to the symphony-form. Even if – according to the modern history of music standards and preconceptions –top rank composers cannot be found in both these two orchestras, amongst them dwelled the awareness, the wisdom and the hardihood of an Army of Generals, paraphrasing Charles Burney's quotation16.
Amongst the Petronian generals, Torelli is the composer who gave the most prominent impulse to the concerto-form. During the first years of employment in the musical chapel of San Petronio, under the chapel master Giovanni Paolo Colonna, Torelli distinguished himself not only as a player but also for his compositions, quickly becoming the composer in charge for most of the instrumental music that had to be performed by the musical chapel, as it is confirmed by his numerous instrumental works held in the Archive of San Petronio (more than 80) and by the salary increase of lire 5.12 that he received in 1688.
The instrumentation, the compositional expedients and structural forms adopted for the compositions that he wrote for San Petronio reflect the attention to the specific location for which they were intended. The church of San Petronio is one of the biggest in Europe, the fourth biggest in Italy: 132 metres long, 60 metres wide, 44.27 metres high, this peculiar indoor space presents several characteristics to be taken into account. The sound resonates in the interior with 12 seconds of reverberation delay, due to the massive dimensions of the space. The persistent resonance in the naves produces natural overtones, in such a way, for instance, that if two notes at a distance of a fifth are played, an audible major third will be generated in the nave, making the use of the Picardy third an acoustic necessity. Furthermore, there is a rapid decay of bass frequencies, which makes unavoidable the use of many more forces in the bass instruments and in the continuo sections in order to maintain audibility. Lastly, two different acoustic spaces can be distinguished in the interior: the choir and transept, situated in the middle of the horseshoe shape created by the balcony above where the musicians were located, from where the result of a musical performance is pretty clear - this was the space where the most prominent secular and religious authorities took place; and the naves, in which the sounds come across much more confused and mingled - this was the space occupied by the rest of the assembly. The instrumentation, the compositional expedients and structural forms adopted for the compositions that Torelli wrote for San Petronio reflect the attention to the specific location for which they were intended.
For this reason, a privileged instrument in the acoustic of this church is the trumpet, with its bright and distinct tone that stands out amongst the timbres of the string instruments and the organs. Compositions for the trumpet, to be performed in San Petronio, were written already in the years in which Maurizio Cazzati was the chapel master (1657-1671).
In the wake of this tradition, Giuseppe Torelli wrote several compositions for one, two, four trumpets and strings, adding also oboes and bassoons in the second period of his employment in the musical chapel (from 1701). Torelli adopted a musical form for these compositions which is not the traditional sonata da chiesa structure (4 movements: slow, fast, slow fast), still used in Bologna by Domenico Gabrielli or Giuseppe Jacchini. Torelli's trumpet compositions (indifferently labelled as Sonata, Sinfonia, Concerto) present a general pattern which can be considered the basis for most of the composer's orchestral works, and more specifically for his concertos. We can call this form 'abstract', since the structure of the movements is not related to dances, and it consists of three movements, in which the second one is multi-sectional. Marc Vanscheeuwijck described it in this way:
The central part of the composition only rarely includes a trumpet part: generally, it consists of a virtuoso solo section for one or two violins with scales and/or broken chords in fast tempo, symmetrically preceded and followed by a melodically and harmonically related tutti section. Often the form of this middle movement in three sections recalls the structure of a da capo-aria (ABA or ABA'). The first and final movements, always including trumpet(s), are most often set in a structure akin to the ritornello form17.
The fast external movements do not present a fixed contraposition of tutti ritornelli andsolo episodes according to a specific harmonic pattern (as Vivaldi, amongst the others, often did). Torelli, instead, made use of the so-called principle of alternation, a fundamental main feature in the vocal and instrumental repertoire in San Petronio. Widely applied by Franceschini, Colonna and Perti it consists in the contraposition of imitative and fugal counterpoint with passages in homophonic counterpoint. In his trumpet compositions, Torelli often subdivided the instrumental ensemble in concertino and concerto grande, providing a variety of dynamic contrasts and different timbre solutions.
It is problematic to draw a possible evolution in the setting used by Torelli during the years of activity in San Petronio, since most of the manuscripts held in the Archive of the church are not dated. It is clear, nevertheless, that Torelli dedicated himself to the experimentation of different setting solutions (varying the number of soloists from 1 up to 4), while establishing the above-mentioned structure as the compositional form.