DAVID AND THE USE OF IRON: http://followtherabbi.com/journey/israel/iron-of-culture1
Traditionally all the Psalms were thought to be the work of David, but many modern scholars see them as the product of several authors or groups of authors, many unknown. Most Psalms are prefixed with introductory words (very different in the Masoretic and Septuagint traditions) ascribing them to a particular author or saying something about the circumstances of their composition; only 73 of these introductions claim David as author. Since the Psalms were written down around the 6th century BC, nearly half a millennium after David's reign (about 1000 BC), they doubtless depended on oral tradition for transmission of any Davidic material.
Psalms 39, 62, and 77 are linked with Jeduthun, to be sung after his manner or in his choir. Psalms 50 and 73-83 are associated with Asaph, as the master of his choir, to be sung in the worship of God. The ascriptions of Psalms 42, 44-49, 84, 85, 87, and 88 assert that the "sons of Korah" were entrusted with arranging and singing them; 2 Chronicles 20:19 suggests that this group formed a leading part of the Korathite singers.--Wikipedia
Oxford Companion to the Bible ...
Modern scholarship is skeptical about two aspects of the traditional titles: authorship (hence dating) and setting. There is no hard evidence for Davidic authorship of any of the psalms. David’s reputation as a musician (1 Samuel 16.23; Amos 6.5) makes it reasonable to associate him with the psalms, but it is not possible to prove authorship. As regards the setting, modern scholarship is much more modest in its claims. The ancients were overspecific. Rather, one can only describe the setting in a very generic way: a lament of an individual or community, a song of praise in the Temple, and so on. In other words, literary classification has replaced the historicizing tendency that the titles display.
--ROLAND E. MURPHY, O. CARM