1 Psa 33:1-22. A 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.
The sentiment falls in with Psa 32:11 (compare 1Co 14:15). The instruments (Psa 92:3; Psa 144:9) do not exclude the voice.

3 a new song - fresh, adapted to the occasion (Psa 40:3; Psa 96:1).
play skilfully - (Compare 1Sa 16:17).

4 Reasons for praise: first, God's truth, faithfulness, and mercy, generally; then, His creative power which all must honor.

6 In "word" and "breath" - or, "spirit," there may be an allusion to the Son (Joh 1:1) and Holy Spirit.

9 he spake - literally, "said."
it was - The addition of "done" weakens the sense (compare Gen 1:3-10).

10 In God's providence He thwarts men's purposes and executes His own.
heathen - literally, "nations."

12 The inference from the foregoing in Psa 33:12 is illustrated by God's special providence, underlying which is His minute knowledge of all men.

13 looketh - intently (Isa 14:16).

15 fashioneth - or, "forms," and hence knows and controls (Pro 21:1).
alike - without exception.
considereth - or, "understands"; God knows men's motives.

16 Men's usual reliances in their greatest exigencies are, in themselves, useless.

17 On the war horse (compare Job 39:19-25).
a vain thing - a lie, which deceives us.

18 Contrasted is God's guidance and power to save from the greatest earthly evil and its most painful precursor, and hence from all.

20 waiteth - in earnest expectation.

21 his 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).