Psalm 47 - All ye the peoples, Clap the hand!
I believe this Psalm is about the glorious celbration when all Israel shall be restored to the Lord and united with the church at the end of this age.
v1 - "free singing" is literally 'voice of song". It is a song sung while being beside oneself. see Ps 17:1 note.
This psalm is concerning the nations' relationship with God.
v2 - God is King over all the earth, not just Israel (Rom 3:29).
v3 - Who is the "us" and "our feet"? This "us" includes the peoples in v1. They are singing this.
Many from among the nations will become part of Israel, and many will not. The peoples and nations mentioned here in this verse are those who do not become part of Israel.

I followed LXX and Leupold to translate the imperfect verb "subdue" as past tense because, as Leupold says, the verb is in the waw-consecutive form without the waw, which would make it reverse its tense.
v4 - The inheritance of Jacob, God's beloved and chosen, has become the inheritance of the peoples who are beside themselves singing in v1.
This is followed by the only selah in the Psalm. That God chooses our inheritance for us is something we need to ponder and appreciate (Ps 16:5-6 & note).
v5 - This is a quote from 2Sam 6:15, where the Ark of the Covenant was brought up from Obed-Edom the Gittite's house to Jerusalem amid shouting and trumpets.
What does the Ark of the Covenant being returned to Jerusalem have to do with the gentiles rejoicing? Why would the gentiles be singing about this?
Obed-Edom was a Gittite, that is a Philistine gentile, who apparently had become an Israelite proselyte. The name "Obed-Edom" means "slave of Edom",  indicating that Obed-Edom had been sold as a slave to Edom, but had escaped to Israel (Deut 23:15-16) or was freed by Israelite armies (1Sam 14:47).
Why was the holy Ark of the Covenant dwelling in the house of a converted gentile? After God killed Uza for touching the Ark to keep it from falling during David's 1st attempt to bring up the Ark, no Israelite would allow the Ark on his property.
The Ark needed a place to stay, but no Israelite would accept it after seeing what had happened to Uza. The only person willing to accept it was Obed-Edom, the Gittite, a Philistine proselyte.
God visibly blessed the family of Obed-Edom during the 3 months that the Ark abode there (2Sam 6:11-12). This made Israel jealous (Rom 11:11-14). Why is a gentile getting the blessing from our Ark of the Covenant?
After David brought the Ark up to Jerusalem, Obed-Edom and his household stayed on as Levites taking care of the Ark (1Chron 15:18-24; 16:5-38; 26:4-15).  How could this be? I think they saw that since he was blessed in taking care of the Ark, he was made a Kohathite by divine inspiration by the High Priest.
Why are the gentile and Jewish Christians singing about this event? I think it is because it is a figure of the future event to come, when the times of the gentiles ends, and God's testimony is returned to Jerusalem from being with gentiles during the gentiles. This will be a wonderful celebration (Rom 11:15).
v6 - 4 times "Sing psalms" in 1 verse!
v7 - God is King of all the earth, not just of Israel (Rom 3;29-30). This verse exhorts Israel to understand this, that God has a plan for the gentiles to be included in God's chosen people (Acts 10:45;11:18; Eph 3:4-6).
We understand a lot of truth by singing it. This psalm is simple, yet profound.

Sing a didactic Psalm. Sound doctrine praises God. Even under the economy of types and ceremonies, it is clear that the Lord had regard to the spirituality of worship, and would be praised thoughtfully, intelligently, and with deep appreciation of the reason for song. - C. H. Spurgeon
v8 - God is mentioned as King and reigning 5 times in this short Psalm (vv2,3,6,7,8).
v9 - "the peoples" are all nations including Israel.
I think "gathered together" refers to the rapture (see note & refs on Ps 50:5).
These willing-hearted from among the peoples are the one people of the God of Abraham.
I translated the Hebrew word magan as "offerers" as in (Prov 4:9; Gen 14:20; Hos 11:8). The willing-hearted among the nations are those who have offered themselves as a living sacrifice to God (Rom 12:1).
The last sentence of this Psalm says literally "he was taken up very high". Most translate it as "God was taken up very high", which would mean that God is lifted up by our praises as in Ps 97:9, which uses the same Hebrew phrase.
I took the singular pronoun "he" to refer back to "the people of the God of Abraham", who have been raptured. "They've been taken up on high" indicates that God accepted their offering (Rom 15:16).

-copyright Steve Miller 6/21/2020