A Psalter is a book of Psalms to be sung in churches, arranged in meter to suit particular tunes. Growing up in the gospel hall and mission hall world - where there was a fair bit of time spent speculating about the future rather than understanding the past - we didn't use a Psalter, we used the Believers Hymnbook on Sunday morning and Redemption Songs the rest of the time, both of which were full of centuries-old hymns, as well as other more recent ones from the late 1800s and early 1900s. However I was struck to discover that the 1650 edition of the Psalter remained as the standard until it was revised in 1929.
When the 1650 edition was being prepared, the Church of Scotland appointed a group of six ministers to review the work. First on the list (recorded on p 288 of Treasury of the Scottish Covenant) is James Hamilton of Ballywalter, who at this time was ministering in Edinburgh. Also among the six were Robert Trail (whose brother William was a minister at Ballindrait in Donegal) and Hew McKail (whose father Matthew had been in Ulster in early 1644 - but I can't find my reference to this at the moment).
The critics of Ulster-Scots usually focus on the Plantation of Ulster of 1610 and infer it was a one-way single event from which all of the subsequent ills of Ireland have grown, usually with the subtext of alleged invasion and dispossession of the native Irish. In the Plantation (in addition to other allocations to "servitors", the church and the London companies) 59 Scots were granted 81,000 acres / 51 Englishmen were granted 81,500 acres / 280 Irishmen were granted 94,000 acres.
However, the reality is that there has been an ongoing two-way flow for (at least) four centuries between Scotland and Ulster. Even today, a quick spin down my Facebook friends list shows that a lot of people I went to school with ended up settling in Scotland. The 1650 Psalter is another example of this exchange, with clear Ulster fingerprints on its' production.
PS: There's a chronology of the Psalter here on Wikipedia and an excellent in-depth article here by Rev David Silversides of the Reformed Presbyterian Church in Loughbrickland, County Down