Liland, good catalogs of individual songs and poems in manuscripts is a relatively recent developement in National libraries. Oxford started earlier, but only published theirs in 1969. I heard about 3 years ago from the keeper of manuscripts in the Folger Shakespeare Library that the British Library had finished theirs, but I haven't see any publication yet. Folger has a good 'in house' one as a first line indexed card file, but no published one. Before that it depended on how good the librarian was at remembering the material they had. And they sometimes missed the boat. NLS MS 6299 is described by in the NLS catalog as a collection of Scots songs copied from Ramsay's 'Tea Table Miscellany' and Herd's 'Scots Songs'. Many songs are in TTM, but they don't have the same titles, and some are a bit different. It takes little study of the manuscript to discover that it was finished about 20 years before Herd's 1st book (1769) appeared.
Where did that "Geordie" come from? The more modern "Auld Lang Syne" tune was in the overture to Wm. Shield's 'Rossina' in 1783. Early commentators who knew not the history of the tune took it as Shield's composition. Shield was from Northumberland. He is apparently the 'Geordie'. At any rate a close variant appeared earlier as "The Miller's Wedding" in Angus Cumming's 'Strathspeys', 1780, and as "The Miller's Daughter" in McGlashan's 'Strathspey Reels', c 1778. This is in turn a variant of "The Miller's Wedding- Strathspey" in Bremner's 'Reels', p. 41, 1758. According to James Dick it was Burns who contributed "O can you labour lee" to 'The Scots Musical Museum', #394, where the tune may be found. "Coming through the rye" SMM #417 (song by Burns), and #418 (older set of verses) are two more variants of the tune. Niel Gow gave the "Auld Lang Syne" tune as "Sir Alexr. Don's Strathspey" in bk. 1 of 'Strathspey Reels', 1784.
John Glen in 'Early Scottish Melodies' p. 189, gave the tunes from Cummings/McGlashan, 'Rossina', "Sir Alex. Don's Strathspey", and that given by Thomson with Burns' "Auld Lang Syne" in 1799. [ABCs of most of these are in file S2.HTM on my website.]
Incidently, James Johnson in the Preface to vol. 5 of SMM, where Burns' "Auld Lang Syne" appeared to the old tune as #413, made a statement that the 'Z' would not appear in the index to vol. 5. 'Z' meant an old song with corrections or additions. However, in that volume the 'Z' at the end appears in addition on SMM #467, "As I came o'er the Cairney mount" (Burns' polite and drastically revised version of a song in 'The Merry Muses', with nothing but the 1st two lines, and the 1st line of the chorus left from the 'Merry Muses' song) and on SMM #478. The latter is "Kind Robin loves me" and except for a word added in one line (to fit the meter of the tune) and full chorus spelled out, it's the same as in Herd's 'Scots Songs', I, p. 311, 1776. 'Z' here obviously means a very slight correction. [See 17th century broadside ballad 'original' as "Scotch Moggy's Misfortune" in Scarce Songs 1 on my website. It's undoubtably based on a Scots song no longer extant, and not truly the 'original'. There's more than one polite imitation under the same title.] That 'Z' doesn't appear at all in vol. VI of SMM. Interpreting the 'Z' as always indicating that an old song was substantially altered, or added to, is a mistake. In addition to the above 'Z' appears on SMM #140, #156a and b, #227, #277, #292, and #321.