When sound engineers mix an album, they decide what level of sound they want for each track. Depending on the intentions of the artist, they might want one track to be slightly quieter than another to add to the overall atmosphere.
The effect is even more marked between albums, especially those from different eras. The 70s albums are normally mixed so that they are slightly quieter than the 00s albums, if your stereo is set to exactly the same volume. Standard practices have just changed over time.
By default, Spotify solves all of this by automatically equalizing volumes between tracks. If your volume is set to 11, each song sounds as loud. If it is set to 1, they will all be silent. For the most part, that 's a good thing, but if you want to hear each song how the creators originally mixed it up, you can turn off that feature. Here's how.
On your computer
Open Spotify, click the down arrow next to your name and select Settings.
Scroll to the end and click Show Advanced Settings.
Under Playback, turn on the Set the same volume level setting for all songs.
Now the songs will each play on their own volume.
On your smartphone
Open Spotify and access your library. Tap the Settings icon at the top right and select Play.
Disable the Enable Audio Normalization setting.
Now, each song will play according to the volume at which it was mixed.