One of the main expressions of fervent love is that the lover sings songs of love — so should we sing before God. (Sefer Haredim, chap. 34).
It is the way of one who loves passionately to sing. Since the love of our Creator is so great, even beyond the love of women, someone who loves Him with all his heart will sing before Him as sang Moses and the Children of Israel, and Miriam and Deborah and Joshua, and the sons of Korach, and David and Solomon, all with the holy spirit. (Sefer Haredim, chap. 9, #6)
— Rabbi Eleazar Azikiri in Jewish Spiritual Practices by Yitzhak Buxbaum