There are three equations that determine the difference or relationship between the keys of two different songs. I use three simple mathematical equations of 3x, 3x + 1, and 3x - 1 which each describe the song key's distance from the key of another.
These days I usually put musical albums into one of the two categories A and B. On albums placed in Category A, at least one of the album's first three tracks besides track #02 must be played in a key whose distance from said track's key is a multiple of 3, complying with the 3x equation. If the second track is the only one of the three tracks that complies with 3x, the album will have to be placed in Category B.
Note that the track key's distance from that of track #02 (referred to here as the "target key") by 5 half-steps is determined by how the titles of certain tracks are formatted. The songs written in bold italic are the ones played in the same key as the second song. The ones written in bold are played in a key that's close, like G# Major or F# Major, if the second track's key is C# Major. The ones left unformatted are played in a key that's two half-steps away from the second track's key, which is a little bit close to that key. And the ones slashed out are played in a key whose distance is from the second track's key is perfect.
Also, notice the "-" and "+" symbols. A "-" indicates that the song is about a quarter-tone below its stated key, and a "+" indicates that the song is about a quarter-tone ABOVE the key.