  Studying stellar pulsations in open clusters offers the possibility to
perform ensemble asteroseismology. The reasonable assumption that the cluster
members have the same age, distance, and overall metallicity aids in the
seismic modelling process and tightly constrains it. Therefore it is important
to identify open clusters with many pulsators. New pulsating stars of the Beta
Cephei type were searched for among the members of the open cluster NGC 637.
Thirty-one hours of time resolved V filter CCD photometry were obtained. The
measurements confirmed two previously known variables, and revealed three new
Beta Cephei stars plus one more candidate. All four pulsators have amplitudes
high enough for easy mode identification and are multiperiodic. With four
certain pulsating members, NGC 637 is now among the six open clusters richest
in Beta Cephei stars. It is thus an excellent target for ensemble
asteroseismology, and to tackle the question what separates pulsating from
apparently constant stars in the Beta Cephei domain.
