'Urah hanevel v'chinor a'ira shachar' Awake, neivel and harp, I shall awaken the dawn Psalms 108:3
- From Artscroll Psalms pg. 1320-1
David exclaimed in this verse, "Other kings slumber soundly through the entire night and are awakened by the dawn and its rays of light. I, however, awaken the dawn. A harp stands over my bed. At midnight, a north wind blows through my chambers and causes the harp to play by itself. These sounds awaken me and I spen the rest of the night singing pslms and hymns of praise to G-d. (Rashi)
Similarly before the dawn of the Messianic redemption, there will be a universal revival of the Jewish spirit. Then Jews will perceive the presence of G-d despite the engulfing gloom of exile.
The commentaries to the Talmud (Berachos 3b) attempt to explain the phenomenon of the harp and the wind. Rav Hai Gaon says that David's harp functioned like a wind gauge or anemometer. At midnight, the wind would come from the north and reach a certain velocity. David's harp was positioned in such a way as to catch this northerly wind and record its speed through the vibrations of the harpstrings. When the wind reached a certain predetermined velocity, David knew immediately that midnight had arrived.
Rashba describes this harp as a complex apparatus which resembled a water clock. Drops of water were released into a receptacle according to a precise schedule. The drops were released through the night, until a t midnight the contatiner was full. The full weight of the receptacle activated a mechanism which automatically strummed the harp strings and awakened David.