A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
psa 33:1A call to lively and joyous praise to God for His glorious attributes and works, as displayed in creation, and His general and special providence, in view of which, the Psalmist, for all the pious, professes trust and joy and invokes God's mercy. (Psa. 33:1-22)
The sentiment falls in with Psa 32:11 (compare Co1 14:15). The instruments (Psa 92:3; Psa 144:9) do not exclude the voice.
psa 33:3a new song--fresh, adapted to the occasion (Psa 40:3; Psa 96:1).
play skilfully--(Compare Sa1 16:17).
psa 33:4Reasons for praise: first, God's truth, faithfulness, and mercy, generally; then, His creative power which all must honor.
psa 33:6In "word" and "breath"--or, "spirit," there may be an allusion to the Son (Joh 1:1) and Holy Spirit.
psa 33:9he spake--literally, "said."
it was--The addition of "done" weakens the sense (compare Gen 1:3-10).
psa 33:10In God's providence He thwarts men's purposes and executes His own.
psa 33:12The inference from the foregoing in Psa 33:12 is illustrated by God's special providence, underlying which is His minute knowledge of all men.
psa 33:13looketh--intently (Isa 14:16).
psa 33:15fashioneth--or, "forms," and hence knows and controls (Pro 21:1).
considereth--or, "understands"; God knows men's motives.
psa 33:16Men's usual reliances in their greatest exigencies are, in themselves, useless.
psa 33:17On the war horse (compare Job 39:19-25).
a vain thing--a lie, which deceives us.
psa 33:18Contrasted is God's guidance and power to save from the greatest earthly evil and its most painful precursor, and hence from all.
psa 33:20waiteth--in earnest expectation.
psa 33:21his holy name--(Compare Psa 5:12; Psa 22:22; Psa 30:4). Our faith measures mercy (Mat 9:29); and if of grace, it is no more of debt (Rom 11:6).