Psalms of Moshe: 98:5: Sha’arei Chaim
“Play music to God on a harp, with harp and sound of chanted praise.” There is a debate over which form of praise is considered more elevated: Voice or musical instrument. This verse indicates that voice comes to enhance the instrument, which is more elevated. (Sha’arei Chaim)
We sing Kabbalat Shabbat to enhance the “Musical Instruments” of the Angels playing in the Beit Hamikdash in heaven.