"set the same volume level for all songs" in spotify, does not take into account the subtle volume transients of an album that audio engineers have spent hours working on!
Solution - Add an option in settings for "Set The Same Volume Level Based On Albums". This will retain the intended volume differences between songs on an album (similar to the way replaygain album mode functions).
"Set The Same Volume Level Based On Albums"(replaygain album mode) DESIGNED TO RETAIN THE SUBTLE VOLUME DIFFERENCES BETWEEN TRACKS ON AN ALBUM)
This solution is extremely quick for spotify developers to implement - Just take the individual track volume values in an album and you already have this information due to your "set the same volume level for all tracks", then get the average of these track volumes for that album and the result is your per album volume reduction value! Albums will finally sound like albums again.
IN THE FUTURE - When you select "set the same volume for all albums" then it should also read the metadata in your personal music files (when the tag is present). The Name of this tag in my mp3 and flac collection is "REPLAYGAIN_ALBUM_GAIN".
"Set The Same Volume Level For All Tracks" - (replaygain track mode) BEST FOR SHUFFLE MODE, OR LISTENING TO LOTS OF RANDOM SONGS)
Spotify already has "Set the same volume level for all tracks" in settings for songs that are streamed, which is the equivalent to replaygain track mode. This currently only works for streamed songs and it doesn't check to see if the tag "REPLAYGAIN_TRACK_GAIN" is present in your local audio file that you're currently listening to, a very simple fix indeed.
DISABLED MODE = NOTHING TICKED.
When unticking "set the same volume for all albums" and "set the same volume for all tracks", all streamed and local music should not play with any volume adjustment on either streamed or library tracks, it is exactly the same effect as disabling "set the same volume for all tracks" that we currently have. There are many reasons for needing to turn of volume normalization (such as troubleshooting volume problems etc). Replaygain volume adjustments should be fully lossless when your dac is 24 bit.
Note to spotify - By using metadata, this should be totally seamless - E.g. If the exact same album is streamed, then local files should play at precisely the same volume as streamed files.
IF EITHER TAG IS MISSING FROM METADATA - "REPLAYGAIN_TRACK_GAIN" or "REPLAYGAIN_ALBUM_GAIN" then spotify should not make any volume adjustment and it should produce the same result as having album mode or track mode not TICKED.
When installing spotify, the default should still be set to "set same volume for all tracks" like it it just now
Updated on 2018-10-05
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We're checking back in, to keep you updated on this Idea.
When you play an album, we normalize the loudness level of that album at the same time.
If you're interested in some further info on this, we'd recommend checking out this FAQ, which we currently have up for artists.
We also have some more information on Audio Settings here.
Under Music Quality, you can switch Normalize volume on, or off.
Right now however, it's not possible to normalize local files. For that reason, we're changing this to case closed, as this isn't something we're going to work on.