You can find a YouTube playlist here with many of the songs suggested below.
Gathering
Singing, we gladly worship the Lord together (CH 257) is a lively Guatemalan which would work as a gathering song while also linking to the Gospel with the line “sow seeds of peace and love”. The spring has sprung (CH 224) also hints at the Gospel with the new buds and new shoots and at the broader theme of new life from Epistle, something we also find in Sing for God’s glory that colours the dawn of creation (CH 172) with its hope of “the new creation to be”. Rejoice! the Lord is King (CH 449 / MP 575), This is amazing grace (CCLI) and King of Kings (CCLI) pick up the idea of the kingdom to come and could also link in with the Old Testament.
Word
May the Lord God hear you pray (PFAS 20C / Jubilate) is perhaps the best option for singing the psalm to a well known tune as it would work with either St Bees or Nottingham. May God draw near when the hour of trouble strikes (CH 11) has a strong combination of words and music but isn’t the easiest tune for a congregation to pick up so would need strong leadership. This could be a good week to sing the psalm responsorially and O Lord, hear my prayer (GIA / Hymnary) is a well known response which could fit.
Response
In our lives plant seeds of hope (CH 349) and The reign of God, like farmer’s field (CH 343) put the Gospel text into the wider context of other stories from the Gospels about seeds while To what can the kingdom of God be compared (link) links the story to other small actions which can bring about the kingdom of God. The kingdom of God (Hope) is a beautiful reflective song on this text and could be led by a soloist with the congregation joining in the last line of each verse. You could use the short chant The kingdom of God is justice and peace (Taizé), perhaps as a response for prayers, or God our Father (Let your Kingdom come) (Resound) which is a setting of the Lord’s Prayer but you could just use the refrain.
By faith (MP 1262 / CCLI / Getty) is rooted around v7 of the Epistle, “we’ll walk by faith and not by sight” while the beautiful Pakistani song O Lord Jesus, enfold me in your arms (CH 571) also picks up the theme of faith, including the need to “persuade others” in v11. The chorus of One more step along the world I go (CH 530 / MP 1346) would pick up the final verse of the reading, as would Behold, behold I make all things new (Wild Goose) which is a great song to teach in two parts.
There are probably many more songs inspired by David than there are about him. God of the prophets (Hymnary) or Hail to the Lord’s anointed (CH 474 / MP 204) would set the story of David’s anointing into the big picture of the Christian story. As well as the German chorale melody there is a version of the latter for band set to a traditional Irish melody by New Scottish Hymns (New Scottish) and a new version by Indelible Grace (link). You might also pick up v7 with the focus on God looking at the heart and Man looks on the outside (Vineyard) is an all-age song which picks this up explicitly. You could also use songs where we dedicate ourselves to God such as When the music fades / The heart of worship (MP 1016 / CCLI) or Take this moment (CH 501).
Sending
One way to end would be looking towards the kingdom of God which we focused on in the Gospel, but which can also link to the other readings. ‘Thy kingdom come!’ - on bended knee (CH 473) is a good option for those looking for a hymn, Sizohamba naye / We will walk with God (CH 803) is a lively sending song from Swaziland, while Hear the call of the kingdom (MP 1282 / CCLI / Getty) or Build your kingdom here (CCLI) are options for bands. You could also pick up the new creation at the end of the Epistle with Love divine, all loves excelling (CH 519 / MP 449) or The Church’s one foundation (CH 739 / MP 640). While it’s technically a loose paraphrase of the Magnificat, Canticle of the turning (Wild Goose / PFAS 75B / MV 120) also picks up on these themes and the tune should be well known.