Not too long ago, I uploaded a new work by Phil Lehenbauer which used the tune "Ar Hyd y Nos". This piece is Dutch organist, Klaas Jan Mulder's realisation of the Welsh tune. Mulder was church organist at the Dutch Reformed Church in Kampen and a prolific recitalist, presenting an average of 200 concerts a year.
Score: https://www.sheetmusicplus.com/en/product/improvisaties-14-21025983.html?aff_id=478282