---and a third vote for Jean Redpath. Jean spent some time in the States--Montana, I think---and did some intensive research in cahoots with an American called Serge Hovey. They compiled several volumes of Burns' songs, all of which are sung by Jean using what was decided to be the original tunes as chosen/approved by the Poet himself. Two well-known examples are "Auld Lang Syne" and "Robin of Kyle" [to the tune "Dainty Davie"]. Highly recommended to any Burns fans.
Kenneth McKellar? Aye---a grand singer, and a fair exponent of Burns songs---as long as said songs are suitable for singing by "operatic/Italian" trained voices. Ken actually improved dramatically after doing a t.v. mini-series with Alastair MacDonald and the above-mentioned Jean Redpath.