O come let us sing unto the Lord; *
Let us heartily rejoice in the strength of our salvation!
Let us come before his presence with thanksgiving; *
And show ourselves glad in him with psalms!

Except, no, don’t say that today.  I often forget this until it’s too late… today is the 19th day of the month, which means that Psalm 95 is one of the psalms appointed in the traditional 30-day cycle.  If you use it as the Invitatory Psalm then you’re stuck saying it twice.

I mean, hey, there’s nothing wrong with that; and if you’re game, power to ya.  But there is a background here which may (or should) inform your decision.  The Prayer Books have always had a choice of Invitatory Psalm, but always for a precise reason.  The rubric introducing it in the 1662 book explains:

Then shall be said this Psalm following: Except on Easter Day upon which another Anthem is appointed: and on the nineteenth day of every month it is not to be read here, but in the ordinary course of the psalms.

The “other Anthem” appointed for Easter was (and remains in our new book) the Pascha Nostrum, a canticle made from three New Testament passages.  On the 19th day of the month it seems that the 1662 book called for no Invitatory Psalm at all, and Psalm 95 is just read immediately along with the other daily psalms.  But in our prayer book we have three Invitatory options: the Venite (Psalm 95), the Jubilate (Psalm 100), and the Pascha Nostrum.  The 19th day of the month is, in historical context, the appropriate time to use the Jubilate as the Invitatory Psalm.

And if you like to use the antiphons for the Invitatory Psalm, you can use them for the Jubilate.  (Though it is the preference of this Customary that the antiphons be reserved for Sundays and other Holy Days.)