There are several implications in Thirtle’s thesis for the study of the development of the Psalter. Thirtle agrees with many scholars that the original use of several terms in the Psalms titles had been lost before the time of the LXX translation “as is evident from the disordered state in which they are presented even at that age”, and argues that it then follows that these titles must be very old: if the liturgical terms attached to the psalms are archaic, then it is likely that the psalms themselves were also ancient. He concludes from this that almost the whole of the Psalter is very old. However, almost all the Psalms assigned to “the chief musician” and containing musical notations or the על rubric are contained in the first three books, mostly in the Davidic, Elohistic and Asaph collections, and while Gerstenberger asserts that these psalms were redacted in the exilic or late preexilic periods, a case could also be made for at least some of them being written in the monarchic period. We cannot conclude from this, as Thirtle does, that this is evidence for almost the entire Psalter being from the earlier period. It is arguable that the majority of historical titles are from the exilic or post-exilic periods, and the LXX and Qumran provide evidence of a growing later tendency to attribute psalms to David or to at least make connections to Davidic events or themes. The evidence from Qumran in fact, suggests that Books I to III were stabilised by the beginning of the Qumran period and that Books IV and V remained fluid into the first century CE. The almost complete absence of the rubrics למנצח ,עלמות ,על־ששנים ,שגיון, and על in these later books may support Thirtle’s claim that the key to their understanding was lost early, or it could suggest that they were regarded as archaisms and no longer relevant in the period when the Psalter was completed and stabilised.
David Carr refers to the difficulty of dating biblical psalms, specifically the royal psalms, and urges caution in identifying early monarchic materials in the psalms. While proceeding cautiously he follows by noting that, even if some of the psalms originated in the early monarchic period, “they also have undergone centuries of oral-written tradition before being incorporated into the later Hebrew Bible”.
Some aspects of Thirtle’s work are tenuous, such as his identification of גתית gittith (Pss 8, 81, 84) as pertaining to Tabernacles and ששנים shoshannim (Pss 45, 69) to Passover, and that the psalms with these terms in their titles were to be sung on these occasions. However, he argues convincingly that the rubrics למנצח and על indicate that these psalms were intended for cultic purposes, and should be placed as postscripts to the preceding psalms. The evidence from the LXX and Qumran is that the meaning and cultic purposes of these psalm titles were lost early, and that later editors were inclined to add historical headings in a midrashic style. An analysis of the various collections within the Psalter, paying special attention to the placement of these titles, could provide further opportunities for rewarding insights into the editing and development of the Psalter.
 See Thirtle, The Titles of the Psalms, 151-159.
 Thirtle makes an exception for the possibility of Psalm 137 being post-exilic.
 Gerstenberger, Psalms Part 1, 27-30.
 Carr, The Formation of the Hebrew Bible: a New Reconstruction, 386.
 Ibid., 402.