One tag or technical-info field of the track under its upper-case name. A tag with one value is a string and one with several values a string array; technical-info fields are strings. DURATION is always present: the length in seconds with three decimals, such as 215.400. FILESIZE is the size in bytes and appears only when the host knows it, so a file the library has not indexed yet has none. TRACKNUMBER, when the file has no such tag, is taken from a leading number of up to three digits in the file name (07 - Song.flac, (07) Song.flac, [07] Song.flac) and is absent when there is none.
Successful response from
metadata.readByPath.