CHICAGO—Over the past several weeks, longtime Cubs organist Gary Pressy has gradually stopped playing the light ballpark-organ riffs that typically fill Wrigley Field's stands in favor of more broody, chilling songs. "I have to say that lately the sounds coming out of that organ have made me anxious and sad and in no mood to clap along," said season-ticket holder Mike Preston, adding that instead of playing "Hava Nagila" or using his organ to start a "Let's Go Cubs" chant, Pressy will strike an oppressive minor chord and sustain the unsettling tone for up to an entire minute. "Yesterday he played a really slow fugue on 'Take Me Out to the Ball Game' in this dark, funereal key. It was haunting." When asked for comment, Pressy drove reporters away by playing a demented arrangement of "Happy Birthday" on his newly installed 20,000-pipe, seven-story-tall organ.