Italian violinist and composer. He was born probably around 1680, given that by 1694 he was active as a violinist in Rome; he was identified as "Roman" in the title pages of his first five instrumental collections.
Contemporary documents in Rome mention three other musicians named Mossi: Bartholomeo, his father, a viola player, active between 1674 and 1726; Joseph, virtuoso viola and cello player, probably the brother of Giovanni; and Gaetano, a singer in the Papal Chapel, then in the Portuguese cappella reale, it being unknown whether he was related to Giovanni.
Of the musical training of Mossi we know nothing definite; the assertion that he was a student of Arcangelo Corelli is not documented. Presumably Bartholomeo imparted to his son the rudiments of the violin and introduced him to the musical life of the city. The first news of Mossi as a violinist dates back to 1694: the name, followed by "son of Bartholomew," appears in the list of "musicians of Rome, in the year [1694]". In the same period a "Giovannino di Bartholomeo" appears among the violinists in musical performances sponsored by Cardinal Ottoboni in S. Maria Maggiore, in S. Lorenzo in Damaso, and the oratory of S. Marcello. The frequent use of the diminutive "Gioannino" suggests a career as a violinist beginning as a boy; on April 27, 1700 the name appears for the first time in the minutes of the Congregazione dei musici di S. Cecilia with this diminutive; in the same congregation he was then assigned as director (1708 and 1716) and Prefect of festivals (1713). Around 1716 he was appointed as a professor of violin.
In the first years of his performing activity he participated in numerous performances sponsored by important individual Roman patrons and prestigious institutions. "Gioannino" appears as a violinista di ripieno in the award ceremony of the Accademia del disegno di S. Luca in Campidogli April 19, 1703 and May 7, 1705, and there are records of payments of three oratories sponsored by Cardinal Benedetto Pamphili in his private residence and in the oratory of the Chiesa Nuova. From 1704 to 1711 he appears often in the records of S. Luigi dei Francesi. In 1708 he was one of the violinists in the performance of Handel's oratorio La Resurrezione sponsored by marchese Francesco Maria Ruspoli.
In the libretto of a cantata for two voices, In onore del glorioso nome di s. Gaetano (Rome 1711, music by Giuseppe Cardinalino Dragons), we have news of stable employment at the time: the violinist, who figures on the title page as "Poet" of the composition, is "virtuouso" of the Duke of Bracciano, Baldassare Odescalchi. The libretto of the cantata is dedicated to Madame Colbert princess Carpegna. It is not known how long he was in the service of the Odescalchi court; it had to have ended by 1716, when he published his Opus 1, 12 Sonate a violino e violone o cimbalo (Amsterdam, Jeanne Roger), dedicated to the cardinal Wolfgang Hannibal von Schrattenbach, Bishop of Olmutz: the dedication by Mossi does indeed allude to some position of "virtuoso" at the court of Odescalchi. Two later works (VIII Concerti a tre ea cinque instromenti, op. 2 , and VI Concerti a 6 instromenti, 4 violini, alto viola e basso continuo, op. 3) were published by Jeanne Roger in Amsterdam in the 1720s. The absence of dedications leaves open the question whether the Dutch publisher worked from manuscripts supplied by the composer, from unauthorized copies, or possibly - the most unlikely hypothesis - an Italian edition now lost?
In subsequent years (1717-29 and 1733-37), Mossi figures as a musician of the "concertino" alongside Antonio Montanari and Domenico Ghilarducci in several musical productions sponsored by Cardinal Pietro Ottoboni for the Quarant'ore and for the feasts of s. Lorenzo (August 10) and s. Damaso (11 December). The link with Cardinal Ottoboni lasted over the years: Mossi dedicated to him his last work, the chamber sonatas of Op. 6. In 1727 he published in Amsterdam (published this time by Michel-Charles Le Cène, who had married the sister of Jeanne Roger) his Op. 4 - in some specimens listed as Op. 2 - a collection entitled 12 Concerti a quattro violini e violoncello obligati, dedicated to Maria Vittoria Altieri, wife of Nicholas Maria Pallavicini Prince of Gallicano. In November 1727, a few months after the release of this collection, there appeared in Amsterdam his Op. 5 (XII Sonate o Sinfonie a violino solo con il violoncello) without dedication. In 1733, again in Amsterdam, appeared Op. 6 (in some specimens listed as Op. 3) collecting twelve chamber sonatas for violin and cello or harpsichord. The long editorial pause perhaps was caused by health problems that the violinist began to suffer least from 1729, attested in many letters and petitions addressed by him to the Congregazione di S. Cecilia seeking the benefits reserved for needy musicians.
On June 9, 1731 he wrote, he was "since almost three years sick and in pain and for this cause is unfit to be able to earn his food"; with the passing years the requests for help became more frequent and urgent. In 1737 is recorded his last public appearance, in the Borghese chapel in S. Maria Maggiore, again for the Quarant'ore. Subsequently his economic situation became increasingly untenable, perhaps even the worsening "tormenting disease called by 'doctors rickets'". The last request to the congregation dates back to September 1741, the last grant is bestowed on 6 October of the same year.
He died in 1742, at an unspecified date between January 8 and February 8: This is evident from five masses celebrated by the Congregation of St. Cecilia in the latter date.
At least until the middle of the eighteenth century the works of Mossi were known and performed in Europe, thanks to the spread of the editions of Roger and Le Cène.