Conversation so far:
What compositions did György Ligeti do in Hungary?
György Ligeti's largest work in this period was a graduation composition for the Budapest Academy, entitled Cantata for Youth Festival, for four vocal soloists, chorus and orchestra.
Was the composition Cantata for Youth Festival by György Ligeti well received?
Did György Ligeti have any other works besides Cantata for Youth Festival?
One of György Ligeti's earliest pieces now in the repertoire is his Cello Sonata, a work in two contrasting movements that were written in 1948 and 1953, respectively.
Did György Ligeti win any awards?
György Ligeti has won the 1967 Beethoven Prize of Bonn for Requiem, the 1969 UNESCO International Rostrum of Composers, 1972 Berlin Art Prize, and many more.
Are there any other interesting aspects about the György Ligeti article besides his awards?
György Ligeti's Musica ricercata is based on a simple restriction: the first piece uses exclusively one pitch A. Only at the end of the piece is a second note heard.
Was writing Musica ricercata based on a simple restriction hard for György Ligeti to do?
Did György Ligeti have any influences?
Because of Soviet censorship, György Ligeti's most daring works from this period, including Musica ricercata and his String Quartet No. 1 Métamorphoses nocturnes, were written for the 'bottom drawer'.

Question: Why are they daring?
Self-contained rewrite: Why are György Ligeti's works from his Hungary period, including including Musica ricercata and his String Quartet No. 1 Métamorphoses nocturnes, daring?