Question: What was the middle name of the pianist who first performed Prokofiev's Piano Sonata No. 8?
Related documents: [0]  [DOC] Emil Grigoryevich Gilels (sometimes transliterated "Hilels"; , Russian: Эми́ль Григо́рьевич Ги́лельс , "Emiľ Grigorievič Gileľs "; 19 October 1916 – 14 October 1985) was a Soviet pianist, widely regarded as one of the greatest pianists of the 20th century. [END] 
[1]  [DOC] Sergei Prokofiev's Piano Sonata No. 8 in B♭ major, Op. 84 (1944) is a sonata for solo piano, the third of the Three War Sonatas. The sonata was first performed on 30 December 1944 in Moscow by Emil Gilels. [END] 
Answer: 
Grigoryevich
Grigoryevich