Question: Which set of concertos by Baroque composer Antonio Vivaldi was dedicated to Victor Delfin?
Context: Red Priest is a British Baroque instrumental group that was formed in 1997, originally with eleven members.  Currently it is composed of four performers: Piers Adams - recorder, Adam Summerhayes - violin, Angela East - cello and David Wright - harpsichord.  The group is named after the red-haired Italian priest and Baroque composer, Antonio Vivaldi. The following is a list of compositions by the Italian Baroque composer Antonio Vivaldi (1678–1741). The Mandolin Concerto in C major, RV 425, was written by the Italian composer Antonio Vivaldi in 1725 and is often accompanied by "The Four Seasons" (1725).  The music consists of virtuosic treatment of the solo instrument, the mandolin, and the interplay between the soloist and accompaniment of the orchestra.  The demands are considered higher than other concerti by Vivaldi, and the work is one of the most famous mandolin pieces. L'estro armonico (the harmonic inspiration), Antonio Vivaldi's Op.  3, is a set of 12 concertos for stringed instruments, first published in Amsterdam in 1711.  Vivaldi's Twelve Trio Sonatas, Op. 1, and Twelve Violin Sonatas, Op. 2, only contained sonatas, thus "L'estro armonico" was his first collection of concertos appearing in print.  It was also the first time he chose a foreign publisher, Estienne Roger, instead of an Italian.  Each concerto was printed in eight parts: four violins, two violas, cello and continuo.  The continuo part was printed as a figured bass for violone and harpsichord. Antonio Lucio Vivaldi (] ; 4 March 1678 – 28 July 1741) was an Italian Baroque composer, virtuoso violinist, teacher and cleric.  Born in Venice, he is recognized as one of the greatest Baroque composers, and his influence during his lifetime was widespread across Europe.  He composed many instrumental concertos, for the violin and a variety of other instruments, as well as sacred choral works and more than forty operas. His best-known work is a series of violin concertos known as "The Four Seasons". La stravaganza ("The Extravagance"), Op.  4, is a set of concertos written by Antonio Vivaldi in 1712–1713.  The set was first published in 1716 and was dedicated to Venetian nobleman Victor Delfin.  All of the concertos are scored for solo violin, strings, and basso continuo; however, some movements require extra soloists (such as a second violin and/or cello solo).  What is perhaps most extraordinary about "La stravaganza" is Vivaldi's remarkable inventiveness within a defined framework of instrumental and harmonic forces. A set of twelve concertos was published by Estienne Roger in 1716-1717 under Antonio Vivaldi's name, as his Opus 7.  They were in two volumes, each containing concertos numbered 1-6.  Of the set, ten were for violin solo; the other two were for oboe solo.  The authenticity of some of the works included has long been doubted by scholars.  Three are now considered spurious (i.e. not in fact by Vivaldi) for stylistic reasons.  They are: No. 1 in B-flat major for oboe, RV Anh.  143 (formerly RV 465); No. 7 in B-flat major for oboe, RV Anh.  142 (formerly RV 464); and No. 9 in B-flat major for violin, RV Anh.  153 (formerly RV 373). Stabat Mater for solo alto and orchestra, RV 621, is a composition by the Italian baroque composer Antonio Vivaldi on one of the Sorrows of Mary.  It was premiered in 1712. Dorilla in Tempe is a melodramma eroico pastorale in three acts by composer Antonio Vivaldi with an Italian libretto by Antonio Maria Lucchini.  The opera premiered at the Teatro San Angelo in Venice on 9 November 1726.  Vivaldi later revised the opera numerous times for several difference performances throughout the second half of his career. La Serenissima is a British early music/period instrument ensemble founded in 1994 by violinist Adrian Chandler, who has served as the group's director since its creation.  Taking its name from "La Serenissima Repubblica di Venezia" (Italian for The Most Serene Republic of Venice), the ensemble specializes in the music of Venetian Baroque composer Antonio Vivaldi (1678–1741) and his contemporaries.
Answer: "La stravaganza"