Here are some of the most popular melodies for Magein Avot:
Here's a congregational melody written by Israel Goldfarb in 1918 in New York. It was popular in Conservative synagogues in northeastern New Jersey in the 1960s.
Here's the same tune, adapted for use in orthodox synagogues by avoiding the repeated line.
Here's a traditional tune, used by Louis Lewandowsky (among others). It's currently popular in Boston area orthodox shuls.
Here's another variation of the traditional tune, this time preceded by the opening blessing and followed by R'tsei Vimnuchateinu, all chanted in the proper Friday night chant mode, which is in fact called Magein Avot mode. (Notice that this chant mode rests -- starts and ends -- on what to Western ears may sound like the fifth degree of the scale.) This recording is hosted at
a highly recommended resource.
MageinAvot contains paraphrases of the seven blessings of the Shabbat Amidah. It was added after the Friday night Amidah in order to prolong the service. It is inserted between Va-y'chu-lu and R'tsei Vim'nu-cha-tei-nu. These three together sit where a Reader's Repetition of the Amidah would be, if it were not an evening service.
In ancient times, as now, more people came to synagogue on Shabbat than the rest of the week. Those who came only on Shabbat would be the least familiar with the service and would take more time, and there were always some people that would arrive late. By prolonging the Friday night service, they were given an opportunity to finish their prayers with the rest of the congregation, so everyone could leave together. Synagogues were often located outside the precincts of the city, since the rulers did not tolerate Jewish worship within the confines of their municipalities,[i] and as it was dangerous to walk home alone at night outside city walls, leaving at the same time promoted physical safety.[ii]