2

Back up all the songs. Clear the thumbnail cache of Music. (Music folder of Phone memory). Use Windows Phone's desktop app to sync the music. If you want to copy via Explorer you should rearrange your music folder structure as Music Folder > Artist Folder > Album Folder > Songs.


2

Looking at the windows phone store there is an app that supports gapless playback.


1

Unotune player allows a changeable audio playback rate while preserving the pitch.


1

Audiobooked is an app designed for audio-books, with speed control, bookmarks and more.


1

VLC allows you to change the speed of reproduction from 0.5x to 2x, as you can see in this image:


1

VLC for Windows Phone ought to do the trick for you. The default video player in Windows 10 Mobile also lets you do this.


1

I could be wrong (or it could be wishful thinking), but I cant say I've noticed gaps between tracks in Spotify. Granted, it's not just a player, and granted it's a bit pants on WP, but it can play local files in addition to streamed.


1

No, you can't edit playlists on the phone, you can only create a new playlist.


Only top voted, non community-wiki answers of a minimum length are eligible