Task: Question Generation
Input (English): Passage: During Leopold's illness performances were impossible, so Wolfgang turned to composition. According to the writer and musician Jane Glover, Wolfgang was inspired to write symphonies after meeting Johann Christian Bach. It is not clear when this meeting occurred, or when Wolfgang first heard J. C. Bach's symphonies, although he had played the older composer's harpsichord works in his May 1764 royal recital. Wolfgang soon completed his Symphony No. 1 in E flat, K. 16, and started his No. 4 in D major, K. 19 (which Zaslaw concludes was more likely composed, or at least completed, in The Hague). The D major symphony has, in Hildesheimer's words, "an originality of melody and modulation which goes beyond the routine methods of his [grown-up] contemporaries". These are Wolfgang's first orchestral writings, although Zaslaw hypothesises a theoretical "Symphony No. 0" from sketches in Wolfgang's musical notebook. Three lost symphonies, identified in the Köchel catalogue of Mozart's works only by their incipits (first few bars of music), may also have originated from the London period. Other works composed by Wolfgang in London include several instrumental sonatas, the jewel of which, according to Hildesheimer, is the C major sonata for piano, four hands, K. 19d. A set of violin sonatas, with extra flute and cello parts, was dedicated to Queen Charlotte at her request, and presented to her with an appropriate inscription in January 1765. Wolfgang also wrote his first vocal works, the motet "God is our Refuge", K. 20, and the tenor aria Va, dal furor portata, K. 21.
Output (English): What were the names of Wolfgang's two vocal works?