From contemporaneous reviews
“The hazardous political situation in Europe had an unprecedented effect on the seventeenth music festival which the International Society for Contemporary Music held late in April at Warsaw. Many performers were forced to cancel their engagements at the last minute and could not be replaced. A whole chamber music evening was called off because the Czechs, who were to present works by Jerzy Fitelberg, Milan Ristic, Josef Zavadil, Karel Jirac and Vladimir Polivka, were not permitted to attend. The saxophone concertino of Roman Palester was also abruptly removed. Late substitutions for certain conductors and soloists also lowered the level of performance; unfamiliar compositions were heard in an unprepared way that hurt and sometimes even destroyed their true effect.
“A warm surprise was the warm interest evidenced in the festival by the Warsaw public. The great hall of the Philharmonic, the auditoriums of the Conservatory and of the Opera House were filled with attentive people.
“The music covered a wide territory extending from romantic lushness to atonality; indeed the twelve-tone scale was generously represented.”
— Emilia Elsner, “Troubled Warsaw is the host to nations [International Society for Contemporary Music],” Modern Music, volume 16 #4 (May-June 1939), pp. 243 and 246
“Na upadającą Operę nie było pieniędzy, szkoły muzyczne biedują, artyści śpiewacy, nieangażowani, głodują i zmuszeni koniecznością życiową, występują w kawiarniach — a tu? Co za wspaniała, co za cudowna musi być ta muzyka nowoczesna! Jak wielkie jej znaczenie wychowawcze.
“Widocznie gdzieś, ktoś tak myślał. Ale nie myślała tak nasza publiczność; ta zwłaszcza, co na koncerty
uczęszcza, słucha radiowych produkcji i zdaje sobie sprawę z humbugu, robionego przez ludzi małych.”
(“There was no money for the collapsing Opera House, music schools are poor, singing artists are disengaged, starving, and forced by necessity of life to perform in cafes — and here? How wonderful must be this modern music! How great its educational significance!
“Apparently, somewhere, someone thought so. But our audience didn’t think that way; especially those who attend concerts and listen to radio productions and realize the humbug made by small people.”)
— Piotr Rytel, “Festiwal Muzyki Współczesnej,” Warszawski Dziennik Narodowy 5, nr. 104 (1939), p. 5
(English translation assisted by DeepL)