Theological issues related to the definition of a poetic prayer and their surface prosodic forms are complex. In the Traditional Prayer in the Psalms, Aejmelaeus attempted to trace the development of traditional prayers from pre-exilic to post-exilic time. Her observation and assessment of the vocative-imperative-motivation clause pattern employed in the classic Individual Laments deserve attention. Aejmelaeus writes,
The features which were found to recur, the imperative petitions, the address to Yahweh, and the introduction of expressions of complaint or confidence in Yahweh or the like by employment of the connective כי, seems to constitute a basic pattern common to a great number of individual complaint psalms. This pattern may be understood as a basic element or nucleus of which and around which further forms of prayer could in various ways develop or be developed. 
Aejmelaeus claims that the basic vocative Yahweh – Imperative – כי pattern is a typical Hebrew basic mode of expression and it points toward an early Israelite traditional mode of expression in prayers, rather than a late poetic construction. Aejmelaeus suggests calling these psalms traditional prayers. Nonetheless, Aejmelaeus’ claim does not warrant the pre-exilic early date of origin of those psalms, and that the vocative-imperative-motivational clause pattern is not the mode of expression typically used in prayers only (cf. Provs 4:1-2b; 23:19-21). The reasons also are these:
- It is difficult to determine whether the original forms of the psalms in question have gone through extensive late editorial reworks or not, i.e., the final form might be the original or very close to it. Consider Psalms 141 and 143, these two psalms contain the vocative Yahweh-imperative pattern; however, many do not consider Psalms 141 and 143 as having pre-exilic origin, neither do scholars claim that these two psalms contain traces of editorial reworking.
- Late linguistic markers in the psalms in question can argue against the early date.
- While the vocative-imperative-motivational clause pattern might be found in the Psalter, this mode of speech was not used exclusively to address the Deity in poetic prayer but also found in other biblical poetic texts, Proverbs 4:1-2b and 23:19-21 are examples.
- The vocative-imperative-motivational clause pattern does not occur only with the vocative Yahweh since the vocative-imperative-motivational clause pattern in the opening lines of Psalms 54-57 employ the vocative Elohîm.
However, Aejmelaeus’ claims concerning the use of vocative Yahweh – Imperative combination in the Individual Laments cannot be dismissed for the occurrence of this pattern marks the distinctive mode of speech for many psalms, e.g., Psalms 5, 26, 54, and 86.
On a different genre classification suggestion, Craig C. Broyles differentiates two sub-classes within the psalms of lament: 1) in the psalms of the plea, the psalmists address God to request divine intervention, and 2) in the psalms of complaint, i.e., the God Lament, the psalmists complain against God. However, one cannot draw a clear line between Broyles’ God Lament psalms and Petitionary psalms, since petitionary expressions are prevalent, even more prevalent than the God Lament motifs, in the so-called God Lament psalms.
While it is doubtful that one can establish a clearly defined set of criteria differentiating the two classes, a casual reading of the lament psalms can identify those psalms that contain the motif of God Lament and those that do not. Assuming one agrees with Gunkel’s Individual Lament genre designation, there are quite a few Individual Laments that do not begin with the vocative and imperative combination in the opening lines. These are Psalms 3, 6, 7, 13, 22, 25, 28, 31, 38, 39, 42, 63, 71, 88, 109, 120, 130, and 142. Out of this group, a significant number of psalms contain complaints against God (Psalms 3, 6, 13, 22, 38, 39, 42, and 88).
In contrast, one notes that with the exception of Psalms 43 and 102, the Individual Laments that begin with the vocative and imperative combination in the opening lines have no God-lament motif; these are Psalms 5, 17, 26, 35, 51, 54, 55, 56, 57, 59, 61, 64, 69, 70, 86, 140, 141, and 143. Therefore, one may suggest that in the classic Individual Lament genre, generally those psalms containing the vocative-imperative combination in the opening lines are not God-lament psalms, that is they contain no complaints against God motif. It is, therefore, more accurate to describe these psalms as prayer psalms or prayer songs instead of complaint/lament psalms, for these psalms primarily function as petitions/pleas to God for help. Yet, if these prayers are speeches addressed to God for help, then it also implies that these monologues are directed to God’s hearing alone in the petition for removing the crisis or lessening the sufferings of the petitioner. What then can one make of the phenomena of the shifts in the direction of addresses in many of the classic Individual Laments? These are Psalms 54, 55, 56, 57, 59, 64, and 69. These psalms speak to the Deity directly using second-person singular verb forms, and they also speak about the Deity using third-person singular verbal forms in many instances. The question is then to whom the “speaking about the Deity” is directed? 
One logical explanation for such shifting of address from second-person singular to third-person singular with reference to the Deity is that it is a literary phenomenon, i.e., an oblique form of direct address that recurs quite often in biblical Hebrew verse. Another explanation is that the “speaking about the Deity” suggests the presence of background audiences, i.e., in the cultic setting. Some have suggested that the Psalms of Lament were composed for continuing use in liturgical and ritual settings, i.e., primarily communal and not individual.
Further complicating the issues, the change in direction of address does not always involve a change from speech directed to God to descriptive speech about God, i.e., shifts from second-person singular to third-person singular verbal forms in reference to the Deity. One example is Psalm 43; this psalm contains a change of subject in the direction of speech. Psalm 43 starts out with the familiar opening lines and progresses through the structure of a prayer psalm addressing the Deity directly, using second-person singular verb forms (Ps 43:1-3). Nonetheless, it changes the direction of address briefly in v. 4, speaking about the Deity in third-person singular forms (an oblique form of direct address?). The direction of address then shifts again in the ending with self-addressed meditation/motivation expressions in v. 5. As printed in the BHS, can one call the entire composition of Psalm 43 a petitionary prayer?
The quick reading of Psalm 39 will further illustrate the complex phenomena of the shift in the direction of address and the difficulty in interpreting every classic Individual Lament as a single poetic composition of petitionary prayer.
The structure of Psalm 39 is unique; this psalm addresses God using second-person singular forms throughout vv. 5-12 of the psalm. One notes that the familiar pattern of the vocative-imperative-causal clause does not appear at the beginning but at the final paragraph of the poem. There is no commonality in the opening lines in the first half structure of this psalm and the opening lines of many other psalms in the same category.
In this psalm, the opening paragraph is the poet’s self-reflection/meditation that begins with the quotation marker אָמַרְתִּי. Immediately followed the meditation the psalmist addresses God directly using the quotation marker: דִּבַּרְתִּי. The question is then, “Who are the intended audiences in the opening paragraphs of the poem?” The human-Deity direct monologue takes place after v. 4 of the poem. The opening lines of the direct speech, i.e., the complaint against the Deity, vv. 5-7, contain wisdom motifs. The second half of the poem consists of the complaint and the petition mode of speech, which is also in the form of direct speech. Thus, the prayer addressed to God includes only vv. 5-14 of the psalm.
Psalm 39 does not have the familiar structures seen in many classic Individual Laments. The entire poetic composition does not resemble a structure of a petitionary prayer but a composition of self-reflection and prayer. Further, this psalm contains neither the motif of the enemy’s oppression, nor petition for the enemy to be punished, nor praise, nor promise of praise.
The difference in syntactic construction in the opening lines between Psalm 39 and other psalms in the classic Individual Laments is clear.
In the preceding section, I have grouped the selected twelve psalms into two separate groups based on the commonalities in modes of speeches and poetic descriptions (Psalms 5, 17, 35, 86, 141 as one group and Psalms 54, 55, 56, 57, 59, 64, and 69 as the other). These commonalities draw a clear line dividing these psalms into two distinctive groups of petitionary prayers. I suggest calling Psalms 54, 55, 56, 57, 59, 64, and 69 as Petitioner- Elohîm -Overhearers prayer songs since these psalms have the classic prayer style structures. What further sets these seven shift-in-direction-of-address psalms as a group is the employment of the vocative “Elohîm” in the opening line; Elohîm is directly addressed in the background presence of the overhearing audiences. These psalms are pleas to God for deliverance from the persecution of enemies (Psalms 56, 57, 59, 64, and 69), for vindication (Psalm 54), for deliverance from a treacherous friend (Psalm 55).
In contrast to Psalms 54, 55, 56, 57, 59, 64, and 69, the opening lines of Psalms 5, 17, 35, 86, and 141 employ the vocatives “Yahweh.” I suggest calling these psalms Petitioner-Yahweh prayer songs since these psalms are also composed in petitionary prayer style but without a change in direction of address. These prayer songs are pleas to Yahweh seeking divine deliverance from enemies (Psalms 5, 17, 35, 86), or the evil ones (Psalm 141).
 Patrick D. Miller, “Current Issues in Psalms Studies,” WW 5/2 (1986) 132-43.
 Aejmelaeus, Anneli. Traditional Prayer in the Psalms. BZZFDAW 167. New York, New York: Walter de Gruyter (1987) 85.
 Broyles, Craig C. The Conflict of Faith and Experience in the Psalms: A Form-Critical and Theological Study. Sheffield, England: Sheffield Academic Press (1989) 37.
 Craig C. Broyles, The Conflict of Faith and Experience in the Psalms: A Form-Critical and Theological Study (Sheffield, England: Sheffield Academic Press, 1989) 35-51.
 As also Broyles, Conflict, 35-51; and Kraus, Psalms 1-59, 38-42.
 One good discussion concerning the shifts in direction of address is the dissertation by Weldon D. Suderman, “Prayers Heard and Overheard: Shifting Address and Methodological Matrices in Psalms Scholarship,” (Ph.D. diss., University of St. Michael’s College, 2007). In addition, the following recent studies also contain good discussions regarding the topic of change of mood in the psalms of laments: Carl J. Bosma “Discerning the Voices in the Psalms: A Discussion of Two Problems in Psalmic Interpretation,” CTJ 7/43 (2008) 183-212; and “Discerning the voices in the Psalms. Part 2: A Discussion of Two Problems in Psalmic Interpretation,” CTJ 44/1 (2009) 127-170; Karlfried Froehlich, “Discerning the Voices: Praise and Lament in the Tradition of the Christian Psalter,” CTJ 36 (2001) 75-90; Carleen Mandolfo, God in the Dock: Dialogic Tension in the Psalms of Lament (JSOTSup 357; Sheffield: Sheffield Academic Press, 2002); also Federico G. Villanueva, The Uncertainty of a Hearing: A Study of the Sudden Change of Mood in the Psalms of Lament (VTSup 121; Leiden, Netherlands: Brill, 2008).
 Sigmund Mowinckel, The Psalms in Israel’s Worship (2 vols.; trans. D. R. Ap-Thomas; Nashville Abingdon, 1962) 1. 1-22; Gerstenberger, Psalms: Part I, 11-14.