The opening summons to praise takes us far away from the solitary wrestlings and communings in former psalms. Now "The singers lift up their voice, And the trumpets make endeavour, Sounding, 'In God rejoice! In Him rejoice for ever!'" But the clear recognition of purity as the condition of access to God speaks in this invocation as distinctly as in any of the preceding. "The righteous" whose lives conform to the Divine will, and only they can shout aloud their joy in Jehovah. Praise fits and adorns the lips of the "upright" only, whose spirits are without twist of self-will and sin. The direction of character expressed in the word is horizontal rather than vertical, and is better represented by "straight" than "upright." Praise gilds the gold of purity and adds grace even to the beauty of holiness. Experts tell us that the _kinnor_ (harp, A.V. and R.V.) and _nebel_ (psaltery) were both stringed instruments, differing in the position of the sounding board, which was below in the former and above in the latter, and also in the covering of the strings (_v._ Delitzsch, Eng. transl. of latest ed., I. 7, n.). The "new song" is not necessarily the psalm itself, but may mean other thanksgivings evoked by God's meditated-on goodness. But, in any case, it is noteworthy that the occasions of the new song are very old acts, stretching back to the first creation and continued down through the ages. The psalm has no trace of special recent mercies, but to the devout soul the old deeds are never antiquated, and each new meditation on them breaks into new praise. So inexhaustible is the theme that all generations take it up in turn, and find "songs unheard" and "sweeter" with which to celebrate it. Each new rising of the old sun brings music from the lips of Memnon, as he sits fronting the east. The facts of revelation must be sung by each age and soul for itself, and the glowing strains grow cold and archaic, while the ancient mercies which they magnify live on bright and young. There is always room for a fresh voice to praise the old gospel, the old creation, the old providence.