Very little is known about James Kerr, who published a number of collections of tunes in Glasgow, Scotland, in the 1870s and 1880s. Four of these are titled "Merry Melodies", and are among the major reference collections for traditional Scottish music.
Each tune has been transcribed in a separate file. These can be combined into larger files by various software, depending on how you are using them. For volumes 2-4, the single-tune file names have a simple naming convention: VNNN_Tune_Title.abc, where V is the volume numer (2-4), NNN is the tune number (001-447), '_' is a separator, and Tune_Title is the title with '_' for spaces and mixed capitalization that follows the modern practice of major words capitalized. Initial articles arn not capitalized, which makes it easy for software to alphabetize by simply ignoring all characters before the first upper-case letter. This naming scheme produces the same tune order as the book.
Volume 1 is a minor exception, since its tunes aren't numbered consecutively. The simplest file-name scheme that gives the tune order for volume has names of the form VPPSNN, where V (volume) is always 1, PP is the page number (1-52), S is the "segment" number (0-3) to identify the sets of tunes that have increasing numbers, and NN is the number within the segment. Page 26 has some unnumbered tunes, which have been numbered to follow the preceding segment. Segment 0 is used for a few sets that fill an entire page, e.g., page 41 which has "miscellaneous" tunes. Note that some of the "segments" are in several pages, but may not fill their first or last pages. (Yes, it's messy.)
There are a few other unnumbered tunes in the collections. This probably qualifies as "typos", or errors in the original engraving. These have been numbered the same as one of the adjacent tunes, whichever produces the same tune order. This seems to work OK, but means that the tune number by itself isn't always unique.
There are many problems with the dance descriptions. The available printed copies aren't always high-quality historical documents. Punctuation is often lost, periods and commas are difficult to distinguish, and random specks can look like periods. The thin parts of letters, bar lines, note stems and flags often fade or disappear. A few guesses have been made in ambiguous cases.
Inside the tune files, the title capitalization has generally been preserved, which is mostly all upper case. There are a few exceptions: Initial articles ("the", "a", "an" and similar words in other languages) are lower case in the T: header. This is sometimes recommended for computer files, since it makes correct alphabetization easy in different languages by using the rule "Sort on the titles without their initial lower-case letters." There are a few tunes with two titles, and the "OR" between them may be transcribed in lower case when they are obiously two different titles. It's not clear that this is significant for any purposes, but it's a hint to software that the text on either side of the "or" word should be entered individually in lists and databases.
For proofreading, there's a Makefile that combines the tunes into large files that are converted to PS and PDF formats. This is done using two different translators, giving file names that end in "-V1.abc" and "-V2.abc", which approximately mean that they're tested against the ABC versions 1 and 2 "standards". Actually, they're translated by the "jcabc2ps" and "abcm2ps" translators, which basically implement the two standards, each with a selection of extensions wanted by their users. A few tunes need to be transcribed differently for the two, and this is indicated in two ways: The "-V1.abc" and "-V2.abc" suffixes are used on the file names, and the '_' after the initial number is changed to '-' for V1 and '=' for V2. The latter is to make it easy for the Makefile to recognize them and sort them appropriately. If you download the single-tune files, you might want to select the version you want, and simplify the file names.
One thing that causes problems for ABC software is the inconsistent use of repeat symbols. All of the following are found the Kerr books, where "..." represents one or more bars of music:
... :| ... :|
... :|: ... :|
... :|: ... ||
... :|: ... :|:
Any of these may have initial |: repeats, but this is rare. The bar lines
may be thick or thin. Sometimes only the vertical line of 2 or 4 dots
appears, mostly at the left edge of the music. Some of these produce
warnings or fatal errors in ABC "player" software that doesn't understand
what was intended. These have mostly been transcribed as:
|: ... :: ... :|
or:
|: ... :|
|: ... :|
Initial bar lines or repeat symbols are generally used only when there's a
full measure at the start of the tune; if there are "pickup" notes
initially, no bar lines or repeats will usually preced them. But initial
repeats later in the tune are usually retained. This is consistent with a
lot (but not all) of modern printed music notation. In some cases, it's not
obvious what repeat pattern was intended, mostly for the 3rd example above,
and the repeats are transcribed "as is" with a N: line commenting on the
problem.
In any case, repeats should generally be considered optional, and you should repeat phrases however seems appropriate to you. If you're playing for dancing, pick a repeat pattern that fits the dance.
Note that the Merrie Melodies books were printed in "landscape" format, with pages wider than tall (and the books aren't all the same size). This causes problems for formatting, because the lines often have too many notes to fit in a US "letter" or A4 page in "portrait" form, unless you use a very small print scale. I've transcribed most of the tunes with staff breaks that work with the formatters at about a 0.50 scale, which is small but readable to me, and is useful for proofreading on my screen. For your use, you should reformat the staffs in a way that works for your musicians, which will usually be different from this. Staff layout has little actual musical meaning, so musicians with visual problems should start with the ABC and pick a scale and staff breaks that makes the music most readable to them.