Of course, I already mentioned that it's a mix of discography, i.e. chronological list of releases by any given artist irrespective of format, and chart information. I don't include the exact discographical info - versions of songs, B-sides, remixes etc, - only a chronological list of releases: singles, albums and compilations (in order of release). To that the list of countries in which any featured release has charted is attached. First I though to present countries alphabetically but then decided the chart entry date will be more appropriate to give the idea how single or album grew in popularity (or didn't) worldwide.
The chart info is presented in a table and goes like this: first of all, name of a country. Next column features the source of the chart, after that the entry date, peak position (with number in brackets indicating how long it spent at No. 1) and number of weeks in the chart.
There are often several infos for some countries. First of all, it's when the country had two or more charts of equal importance. These are featured chronologically - by entry date. If the single/album charted on the same date then the various charts are placed by descending chart positions. In case these are the same too, number of weeks in the charts decides which chart is featured first. In some rare cases all this info can be the same - then the charts are placed alphabetically.
The charts are chosen by their importance. Of course, the official ones are featured, but if there were more then they are all used (where info is available). For example, USA had three main charts in the 1970s - Billboard, Cash Box and Record World. The same with Italy (Musica e Dischi, TV Sorrisi e Canzoni and RAI Hit Parade), The Netherlands (Nationale Hitparade and De Nederlandse Top 40) etc. The biggest count of charts is for the UK - it had a main chart (I dubbed it by the title of publication - Music Week), but also historically important lists in the papers "New Musical Express" and "Melody Maker". Then there was Record Business/The Network Chart, especially prominent in the second half of 1980s. These are all featured.
Regarding radio charts, I only featured them for smaller countries that had only that one radio chart (usually in addition to the main sales-based list). These were important as a measure of public tastes and give some indication of songs' popularity, even if they didn't reach the sales lists (not to mention they boost the number of chart entries😄). On the other hand, I decided not to use specialist charts based on genres (especially prominent in the USA with their rock/dance/country/etc lists). The main ones are more than enough.
Sometimes records (usually albums, but singles sometimes too) had a second life as a re-release or a different version under the same title. So if it's a re-entry, then the info is featured in the main table. If it's a remix or reissue, then the separate table is created.
Sometimes artists released singles or compilations in specific markets. If these charted, they are placed in the main order by date of chart entry.
These are the main things for an explanation. If some other points arise, I'll add them in time.
