In the autumn of 1942, the new phenomenon of the house concert was introduced into Dutch cultural life. Those artists who had refused to become members of the Kultuurkamer, having thus lost their livelihood, would organize so-called “black evenings” during which performing artists, musicians and others would perform for a small audience in return for a fee.
Initially, the evenings had a certain “underground” quality. Later, after they had become more commonplace, things were more open and relaxed. Many were the mornings, afternoons, and evenings when the well-to-do in particular would open their spacious homes for these concerts. Musicians who had few or no sources of income would be given a certain amount raised by the attendees for their performance. Others, who needed the money less badly, provided their services on behalf of the resistance. In the final period of the war, when daily life was crippled by cold and hunger, those attending the concerts were asked to make a contribution in kind—food or fuel, for instance.
Source: Muziek in de schaduw van het Derde Rijk, de Nederlandse symfonieorkesten 1933-1945 ["Music in the shadow of the Third Reich. The Dutch Symphony Orchestras 1933-1945"], Pauline Micheels; Walburg Pers, 1993