What is clear from scripture, in relation to the musical instruction (Psalms 8, 81 and 84) ' upon Gittith', is an association with Gath, the geographical source of the instrument, where it was designed and crafted. What exactly it was, is not clear from scripture and, therefore, can be regarded as irrelevant. We have been given enough for our spiritual inquiry : we need no more.
Sung worship is expressed God-ward, either privately or corporately, and just as the musician chooses an appropriate instrument to match a particular sung piece, so a singer in regard to heart-worship, will frame the content with a suitable disposition in order to give full expression to what is lifted heaven-wards in song.
Paul twice refers to singing and neither time does he mention physical instruments, nor even the audible noise : he exhorts only with regard to a melodious and gracious heart, Ephesians 5:19 and Colossians 3:16.
Thus it is the heart and the understanding that form the 'instrument' - the humanity - which expresses the content. This instrument is adaptable, for several purposes, and can be framed aright, under the direction of the Chief Musician (who is evidently Christ for, 'in the midst of the church, will I sing praise unto thee' Psalm 22:22 and Hebrews 2:12).
Those who sojourn a while in Gath, and endure the privations thereof, and learn from the affliction, will be able, from their experience, to remember what it was like and to hold that thought as they sing, giving depth of expression to what is breathed upwards to heaven in these three psalms.
In the case of 'Gittith-type' singing, what we know is that all three psalms, 8,81 and 84, are addressed to the Chief Musician : one is titled 'of David', one 'of Asaph' and one 'for the sons of Korah', a range of source and application, therefore not restricted in terms of person and a general application would be reasonable to suppose rather than a close, specific focus to something individualistic.
What is especial about 'Gittith-type' singing will be seen in what is known of Gath in scripture : the type of inhabitants and the history : the capture and release of the ark, the sojourn of King David, and who comes out of Gath.
Gath is the environment of Philistines. It is that which took over the testimony of Israel and absorbed it into itself, leaving Israel destitute of that which made it particular. This trial had to be endured until Samuel was ready to be shown to Israel.
Then King David, in escaping from Saul, hoped to find respite in Gath. But it could not be, there was no place for him there, and he had to dribble in his beard and make himself like a mad man to escape with his life.
Yet out of Gath comes Ittai the Gittite - loyal and faithful and honest and true, who loves the King and will not leave him.
All this and more, for time fails to convey it all.
Psalm 8 is an expression of what God is to the whole earth. 'In all the earth'; 'what is man ?' ; 'all sheep and oxen' ; 'in all the earth'. He is God over all, excellent is his name, and humanity (it is not specified exactly how this shall be) shall have dominion and all shall be under his feet.
Psalm 81 catalogues God's dealings with Israel, all his goodness, yet the disappointment that they would not hearken. Even those who hated the Lord would have shown a submission, had they had the opportunity ; but not so Israel. Yet he would have fed them the finest.
Psalm 84 longs for the courts of the Lord, for the birds nest in the broken down altar, and where the fire of sacrifice should arise, they peacefully bring forth their young. But blessed is he in whose heart (if not in outward reality) are God's ways. They go from strength to strength, increasing. Even one day, when it arrives, is better than a thousand, if spent in the courts of the Lord.
The whole earth, Israel and its failure, the captive people.
In this varied pilgrimage, rises a song, from a melodious heart despite its restrictions. Hope looks, love yearns and patience endures.
(To the Chief Musican, upon my stringed instruments.)