Though his righteous Protestant employers, the town council of Reformation Amsterdam, might shudder at the comparison, Jan Pieterszoon Sweelinck's musical job resembled that of a lounge pianist in our own day. The town engaged him to improvise keyboard music at specified times every day, for a public that could file in and out at will and conduct their own business. He could improvise music based upon free flights of his own imagination or upon popular songs of the day, and even upon classical or religious pieces; he needed to show off his musical prowess while keeping the underlying melody audibly present. He did need to perform this concert of music in the Cathedral. It did not stop him, apparently, from executing lush arrangements of popular love songs, such as his surviving set of four variations on the tune of Unter der Linden grüne (Oner een linde groen).
The clear and repetitive phrase structure of Sweelinck's model song allows for quite a bit of elegant ornamentation, even in the first variation. Each half of the song repeats, and already in the first time through the keyboard artist varies his material a bit in those repeats: he adds fluid passing notes to the repeat of the first half, and a stark set of repeated chords to each iteration of the upwards melodic sequence just before the close. The light two-voiced imitation with which the second variation begins sets the tone, and throughout the variation the listener must pay attention to where melodic fragments next appear. Several such imitative motives stand out by their striking rhythmic character; at least once the emphasis on imitation even leads Sweelinck into chromatic notes that would have been extremely colorful in the tuning of his day. The bass voice closes this variation with a flood of quicker notes, setting the pace for the third variation, which proceeds in nearly relentless motor rhythms. The fourth and final variation becomes a catalog of contrapuntal devices, flitting between parallel and contrary motion, insistent rhythmic motives, and more fluid elaborations, syncopations, arpeggiations, and imitations. Sweelinck makes like Art Tatum.