Although those who daven (pray) regularly rarely think of it in these terms because they take it so for granted, music plays an irreducibly crucial role in Jewish prayer
On the most basic level, if the proper nusach, or musical mode, is being used by a Hazzan or other prayer leader, a knowledgeable Jew will, immediately upon entering a synagogue prayer service, be able to tell whether it is a Shabbat, holiday, or weekday, or, for that matter, one of the High Holidays. The words that make up our prayer book are not “said,” per se, but chanted, according to traditional customs and melodies that often date back thousands of years.
For members of a synagogue, the preparation for the High Holy Days season starts weeks, if not months before Rosh HaShanah.
In some congregations, there are the daily selichot prayers that are recited during the month of Elul that precedes Tishrei, and additions to the daily worship services. There is increased giving of tzedakah and the performance of good deeds. For some, a new machzor; for others, a new outfit.
For rabbis, sermons to write.
For cantors and choirs, melodies to rehearse. For the synagogue itself, there’s also a period of preparation.