Question: Who was the father of the composer of String Quartet No. 15?

full_context: Document 1: String Quartet No. 15 (Mozart): Wolfgang Amadeus Mozart's String Quartet No. 15 in D minor, K. 421/417b is the second of the Quartets dedicated to Haydn and the only one of the set in a minor key. Though undated in the autograph, it is believed to have been completed in 1783, while his wife Constanze Mozart was in labour with her first child Raimund. Constanze stated that the rising string figures in the second movement corresponded to her cries from the other room.
Document 2: Violin Concerto No. 1 (Mozart): Wolfgang Amadeus Mozart's Violin Concerto No. 1 in B-flat major, K. 207, once was supposed to have been composed in 1775 (when Mozart was 19), along with the other four wholly authentic violin concertos. However, analysis of handwriting and the manuscript paper on which the concerto was written suggest that the date of composition might have been 1773. It has the usual fast-slow-fast structure.
Document 3: Luigi Gatti: Luigi Gatti (October 7, 1740 – March 1, 1817) was a classical composer. He was born in Lazise in 1740, the son of an organist, Francesco della Gatta. He was ordained a priest in Mantua. In the 1780s he became Hofkapellmeister in Salzburg and Leopold Mozart showed his irritation at not receiving it himself. Between 1801 and 1804 Gatti helped Mozart's sister, Nannerl to locate unknown pieces by Mozart. He died in Salzburg in 1817.
Document 4: Symphony, K. 45b (Mozart): This work was only known to Ludwig Ritter von Köchel as an incipit in the catalogue of Breitkopf & Härtel, and thus it was placed in the Anhang as K. Anh. 214. Alfred Einstein then discovered a set of parts in the Berlin State Library with the title ""Synfonia Ex Bb...Del Sigr. cavaliere Amadeo Wolfgango Mozart Maestro di concerto di S.A. á Salisburgo"". Wolfgang became the Concertmaster to the Archbishop of Salzburg in November 1769, and was given the title "cavaliere" in July 1770, but as this is a later copy, this information cannot be used for dating purposes. Einstein believed the symphony to date from early 1768 on stylistic grounds; Neal Zaslaw and Gerhard Allroggen believe even earlier dates to also be possible, and Zaslaw dated the symphony cautiously to Salzburg in 1767. Einstein also believed that the symphonies in the catalogue of Breitkopf & Härtel were sent by Leopold Mozart to be published.
Document 5: Biographies of Mozart: Wolfgang Amadeus Mozart died after a short illness on 5 December 1791, aged 35. His reputation as a composer, already strong during his lifetime, rose rapidly in the years after his death, and he became (as he has remained to this day) one of the most celebrated of all composers.
Document 6: Piano Sonata No. 8 (Mozart): Wolfgang Amadeus Mozart's Piano Sonata No. 8 in A minor, K. 310 / 300d, was written in 1778. The sonata is the first of only two Mozart piano sonatas in a minor key (the other being No. 14 in C minor, K. 457). It was composed in the summer of 1778 around the time of his mother's death, one of the most tragic times of his life.
Document 7: Violin Sonata No. 35 (Mozart): It is the last of Mozart's substantial violin sonatas, with the only remaining work he wrote for this combination, the sonata in F, K. 547 of 1788 being more of a sonatina. It is also considered by several authors, including Alfred Einstein, to be part of his last series of three great violin sonatas which starts with the Regina Strinasacchi sonata in B-flat K. 454 from 1784 (his annus mirabilis, the year also of the six great piano concertos 14 – 19 and the quintet for piano and winds) and continuing with the E-flat violin sonata from December 1785. The first movement is a movement in sonata form in 6/8 time, with more evenly divided contributions between the two instruments than in the earliest of his sonatas, an exposition divided between its two tonal groups (A and E major), and a compact but unwasteful development section.
Document 8: Clarinet Quintet (Mozart): Wolfgang Amadeus Mozart's Clarinet Quintet, K. 581, was written in 1789 for the clarinetist Anton Stadler. A clarinet quintet is a work for one clarinet and a string quartet (two violins, a viola and a cello). Although originally written for basset clarinet, in contemporary performances it is usually played on a clarinet in A or B-flat for convenience's sake. It was Mozart's only completed clarinet quintet, and is one of the earliest and best-known works written especially for the instrument. It remains to this day one of the most admired of the composer's works. The quintet is sometimes referred to as the Stadler Quintet; Mozart so described it in a letter of April 1790. Mozart also wrote a trio for clarinet, viola and piano for Stadler, the so-called "Kegelstatt Trio", in 1786.
Document 9: String Quartet No. 5 (Beethoven): The String Quartet No. 5 in A major, Op. 18, No. 5, was written between 1798 and 1800 by Ludwig van Beethoven and published in 1801, and dedicated to Joseph Franz von Lobkowitz. Beethoven modeled this quartet directly on Mozart's quartet in the same key (K. 464).
Document 10: Mozart's birthplace: Mozart's birthplace (German: ' or ') was the birthplace of Wolfgang Amadeus Mozart at No. 9 Getreidegasse in Salzburg, Austria. The Mozart family resided on the third floor from 1747 to 1773. Mozart himself was born here on 27 January 1756. He was the seventh child of Leopold Mozart, who was a musician of the Salzburg Royal Chamber.
Document 11: Wolfgang Amadeus Mozart: Wolfgang Amadeus Mozart was born on 27January 1756 to Leopold Mozart (1719–1787) and Anna Maria, née Pertl (1720–1778), at 9 Getreidegasse in Salzburg. This was the capital of the Archbishopric of Salzburg, an ecclesiastic principality in what is now Austria, then part of the Holy Roman Empire. He was the youngest of seven children, five of whom died in infancy. His elder sister was Maria Anna Mozart (1751–1829), nicknamed "Nannerl". Mozart was baptised the day after his birth, at St. Rupert's Cathedral in Salzburg. The baptismal record gives his name in Latinized form, as "Joannes Chrysostomus Wolfgangus Theophilus Mozart". He generally called himself "Wolfgang Amadè Mozart" as an adult, but his name had many variants.
Document 12: Violin Sonatas, KV 10–15 (Mozart): Wolfgang Amadeus Mozart's six sonatas for keyboard with accompaniment of violin (or flute) and cello, K. 10–15 were composed in late 1764 in London during the Mozart family's grand tour of Europe. Queen Charlotte (the wife of King George III) commissioned them on 25 October and the works were dedicated on 18 January 1765. They were published as Mozart's "Opus III" by his father Leopold at 20 Frith Street, Soho, London, where the Mozarts lived from September 1764 until after May 1765.
Document 13: Wolfgang Amadeus Mozart: Wolfgang Amadeus Mozart (/ ˈwʊlfɡæŋ æməˈdeɪəs ˈmoʊtsɑːrt / MOHT - sart; German: (ˈvɔlfɡaŋ amaˈdeːʊs ˈmoːtsaʁt); 27 January 1756 -- 5 December 1791), baptised as Johannes Chrysostomus Wolfgangus Theophilus Mozart, was a prolific and influential composer of the Classical era.
Document 14: Franz Xaver Wolfgang Mozart: Franz Xaver Wolfgang Mozart (26 July 1791 – 29 July 1844), also known as Wolfgang Amadeus Mozart, Jr., was the youngest child of six born to Wolfgang Amadeus Mozart and his wife Constanze. He was the younger of his parents' two surviving children. He was a composer, pianist, conductor, and teacher from the late classical period whose musical style was of an early Romanticism, heavily influenced by his father's mature style.
Document 15: String Quartet No. 18 (Mozart): Wolfgang Amadeus Mozart's String Quartet No. 18 in A major, K. 464, the fifth of the Quartets dedicated to Haydn, was completed in 1785. Mozart's autograph catalogue states as the date of composition ""1785. / the 10th January"". It is in four movements:
ground_truth: Leopold Mozart
sub_queries: String Quartet No. 15 >> composer Answer: Wolfgang Amadeus Mozart
Who was the dad of Wolfgang Amadeus Mozart ? Answer: Leopold Mozart