What is the Shar'i ruling on women using microphones for religious chanting that passersby can hear, and for group chanting, and for the accompanying ululations? Is this permissible in the Maliki madhhab?

The basic rule for women reciting poetry or chanting (in praise of Allah or His Messenger) among other women is permissibility, whether the reciter is one or more. There is no harm in them using a loudspeaker, as long as it is in a place where no non-mahram men can hear them. As for reminding and teaching people, it should be done regularly through a permanent weekly program. There is no harm in reminding on special occasions such as the Day of Ashura or Ramadan. However, reviving seasonal occasions with chanting and ululations is a practice that was not known during the era of the Salaf.