Task: Question Generation
Input (English): Passage: It is not clear why, in 1873, Alkan decided to emerge from his self-imposed obscurity to give a series of six Petits Concerts at the Érard piano showrooms. It may have been associated with the developing career of Delaborde, who, returning to Paris in 1867, soon became a concert fixture, including in his recitals many works by his father, and who was at the end of 1872 given the appointment that had escaped Alkan himself, Professor at the Conservatoire. The success of the Petits Concerts led to them becoming an annual event (with occasional interruptions caused by Alkan's health) until 1880 or possibly beyond. The Petits Concerts featured music not only by Alkan but of his favourite composers from Bach onwards, played on both the piano and the pédalier, and occasionally with the participation of another instrumentalist or singer. He was assisted in these concerts by his siblings, and by other musicians including Delaborde, Camille Saint-Saëns, and Auguste Franchomme.Those encountering Alkan at this phase included the young Vincent d'Indy, who recalled Alkan's "skinny, hooked fingers" playing Bach on an Érard pedal piano: "I listened, riveted to the spot by the expressive, crystal-clear playing." Alkan later played Beethoven's Op. 110 sonata, of which d'Indy said: "What happened to the great Beethovenian poem ... I couldn't begin to describe – above all in the Arioso and the Fugue, where the melody, penetrating the mystery of Death itself, climbs up to a blaze of light, affected me with an excess of enthusiasm such as I have never experienced since. This was not Liszt—perhaps less perfect, technically—but it had greater intimacy and was more humanly moving ..."The biographer of Chopin, Frederick Niecks, sought Alkan for his recollections in 1880 but was sternly denied access by Alkan's concierge – "To my ... enquiry when he could be found at home, the reply was a ... decisive 'Never'." However, a few days later he found Alkan at Érard's, and Niecks writes of their meeting that "his reception of me was not merely polite but most friendly.".
Output (English): What is the last name of the person who reportedly listened to Alkan and was "riveted to the spot by the expressive, crystal-clear playing"?