Our faithful annotators gave our collection of "World" music a look this past week, and so far the acceptable consensus seems to be that each piece in it can be reasonably approached as either popular, jazz, or classical music. So, between the various guidelines we've set aside for those genres, we don't need to devise any new special rules for world situations.
Now that the project is several weeks old and we've had a good look at each genre, we have some interesting numbers to crunch. Here's a quick table that gives the average annotation time by genre:
| ----- | | Genre | # of songs | avg time | stdev | | Classical | 58 | 28.3 | 18.3 | | Jazz | 101 | 25.7 | 10.2 | | Popular | 176 | 24.0 | 10.6 | | World | 45 | 29.5 | 9.8 |
There's evidently a good amount of variation in terms of annotation time, but the average annotation time for a song is rather constant. (Note that all annotation times are self-reported, and do not have any bearing on annotators' earnings.)
We can plot the annotation time as a function of song length, and see that there is a very slight correlation between song length and annotation time, but this is most pronounced for unusually long songs, greater than 10 minutes.
Based on annotator comments, we have already decided to set aside songs longer than 12 minutes for the time being; the numbers now show that this was a pretty appropriate threshold. The annotation times for songs shorter than that show that the 30 minutes per song estimate is still very strong; see a slightly zoomed-in version of the same figure below: