Question: For which instrument did this German composer write a textbook, whose portrait was painted by Pietro Lorenzoni in 1765?
Context: William Bell, born about 1734/5, was an English portrait painter originally from Newcastle upon Tyne.  In around 1768 he moved to London, to be a student in the Royal Academy of Arts.  While there, in the year of 1771, he received a gold medal for his painting of Venus entreating Vulcan to forge arms for her son Æneas.  William Bell's best known works were the portraits painted for the family of Delaval, of Seaton Delaval Hall.  These paintings earned Bell the patronage of Lord Delaval, and in 1775 he exhibited two views of Delaval Hall.  A portrait he painted of Robert Harrison, 1715-1802, is displayed in the National Portrait Gallery, London.  William Bell died on 8 June 1794 and was buried 10 June, St Andrew's Church, Newcastle upon Tyne; his death was reported in the Newcastle Courant (14 June 1794) thus: "DIED, Sunday morning, Mr William Bell, an eminent Portrait Painter, whose memory will be esteemed at long as his animated productions remain, many of which bear testimony to his abilities in this part of the kingdom". The Cobbe portrait is an early Jacobean panel painting of a gentleman which has been argued to be a life portrait of William Shakespeare.  It is displayed at Hatchlands Park in Surrey, a National Trust property, and the portrait is so-called because of its ownership by Charles Cobbe, Church of Ireland (Anglican) Archbishop of Dublin (1686–1765).  There are numerous early copies of the painting, most of which were once identified as Shakespeare.  The Cobbe original was only identified in the collection of the Anglo-Irish Cobbe family in 2006, and had until then been completely unknown to the world.  Evidence uncovered by researchers at the Shakespeare Birthplace Trust led to the claim, presented in March 2009, that the portrait is of William Shakespeare and painted from life.  Many scholars dismiss this theory and have provided evidence to identify the portrait as one of Sir Thomas Overbury The portrait has been the centrepiece of two exhibitions dedicated to it: "Shakespeare Found: a Life Portrait" at the Shakespeare Birthplace Trust, Stratford-upon-Avon, from April–October 2009 and "The Changing Face of William Shakespeare" at the Morgan Library and Museum, New York, from February–May 2011.  An illustrated catalogue provides details of the painting and its provenance. Richard Simon (1898–1993) was a German expressionist.  World-famous faces may be buried in oblivion.  This happened to the painter "Richard Simon", pseudonym 'Simmerl', whose portrait on the official poster of 1936 Summer Olympics in Berlin was distributed all over the world. Portrait of Dorothea Berck is a 1644 painting by Frans Hals that is in the collection of the Baltimore Museum of Art.  It depicts Dorothea Berck at age 51, the wife of the prosperous Haarlem merchant Joseph Coymans, whose portrait Hals also painted.  Both paintings were executed on the occasion of their daughter Isabella's wedding, whose marriage pendants Hals also painted. Johann Georg Leopold Mozart (November 14, 1719 – May 28, 1787) was a German composer, conductor, teacher, and violinist.  Mozart is best known today as the father and teacher of Wolfgang Amadeus Mozart, and for his violin textbook "Versuch einer gründlichen Violinschule". Pietro Antonio Lorenzoni (1721–1782) was an Italian painter who is believed to have painted several portraits of Wolfgang Amadeus Mozart and his family: "The Boy Mozart" (1763), his sister Maria Anna Mozart in "Nannerl as a Child" (1763) and a portrait of their father Leopold Mozart (c. 1765).  He arrived in Salzburg, Austria in the 1740s and first wanted to paint Wolfgang and Nannerl.  His protégé, Johann Nepomuk della Croce, painted a Mozart family portrait in 1780. Pietro Negroni (Born in Cosenza c.1505 – 1565) was an Italian painter of the Renaissance period, active mainly in Naples.  He was also known as "Il Giovane Zingaro" and was a pupil of the painters Giovanni Antonio D’Amato and Marco Cardisco, and strongly influenced by Polidoro da Caravaggio.  He painted an "Adoration of Magi" (1541) and "Scourging of Christ" for the church of Santa Maria Donna Regina Vecchia in Naples.  He painted a "Virgin with child and angels and saints" for Sant'Agnello.  He painted a "Virgin and Child" for Santa Croce in Lucca.  He painted in Aversa and Cosenza, and an altarpiece in the church of the Congrega of Mongrassano in Calabria.  He painted a portrait of a young man now at the Galleria Borghese in Rome. Crestano Menarola (1605 - 1687) was an Italian print-maker and painter of the Baroque period.  He trained in Vicenza under Alessandro Maganza, then moved to work in Bassano del Grappa.  He followed the style of Paolo Veronese.  He also painted for churches and palaces, but little of his painted work remains.  He painted for the presbytery in Asiago.  He painted portrait of Federico da Molin for the Audience Hall in the Palazzo Pretorio of Bassano.  He painted altarpieces for the Cathedral and the chapel of Spirito Santo in the church of San Francisco in Bassano.  His son, Marco, was also a painter.  Pietro Menarola, an engraver, was also a member of his family.  A "Sacrifice of Iphigenia", attributed to Menarola is in display in the Pinacoteca of Palazzo Chiericati, Vicenza.  Among his prints, is a "Descent of the Holy Spirit", after a design of Jacopo Bassano. Sir Thomas Exmewe was born in Ruthin, Denbighshire c. 1454 and was a member of the Goldsmiths Company.  He was elected Sheriff of London in 1508 and Lord Mayor of London on 5 December 1517.  He became the first Lord Mayor of London whose portrait is known to have been painted.  The posthumous portrait, dated c. 1550, is now in the collection of the Guildhall Art Gallery and has been attributed to John Bettes the Elder. The Portrait of Pietro Aretino is a portrait of the Renaissance poet Pietro Aretino by Titian, painted around 1545, possibly for Cosimo I de' Medici.  It is now in the sali di Venere of Palazzo Pitti in Florence.
Answer: violin