In 1822, the 13-year-old Felix Mendelssohn entered his life. The Mendelssohn family was at that time staying briefly in Frankfurt and the young Hiller visited them where he was immensely impressed by the playing of Felix (and even more so by that of his sister Fanny Mendelssohn). When their acquaintance was renewed in 1825 the two boys found an immediate close friendship, which was to last until 1843. Hiller tactfully describes their falling out as arising from "social, and not from personal susceptibilities." But in fact it seems to have been more to do with Hiller’s succession to Mendelssohn as director of the Leipzig Gewandhaus Orchestra in 1843.