Tune My Music is a great tool that lets you transfer playlists between music services. 

It Supports Spotify, TIDAL, Apple Music, YouTube, Amazon Music, Pandora and many more

Receiptify creates for you a receipt of your most listened songs of the last month/last 6 months and all time. 

It connects with spotify, apple music and last.fm

Music-Map creates for you a map of artists similar to an artist that you like based on people's opinions. 

The closer two names are, the greater the probability people will like both artists.

Wish "STAY" by Justin Bieber and the kid LAROI lasted longer?

No problem, this website will stretch out a song in order to make it longer. It simple adds and replace the same parts of ...

Chosic is a website with different free music tools to help you discover new music and analyze your spotify account.

Some of the tools include: Similar songs finder, Your spotify account stats, new music releases etc.

Dubolt  helps you discover music with the help of old favorites 

If you search for an artist or for songs, the website will give you good suggestions based on what you like.  

You can also choose the number of tracks, the tempo, the energy etc...

Magicplaylist creates a whole playlist out of a song that you search

The same does Spotalike

Gnoosic recommends you artists based on 3 ones that you already like.

For every reccomendations, it will ask if you like it, don't like it or if you don't know. It will learn your preferences giving you better reccomendations.