Any accessible app for IOS or Mac to allow manual crossfading between tracks for my Dungeons&Dragons sessions?

So the setup is this... I run games of Dungeons&Dragons... I use music to add atmosphere. I have a range of shuffled playlists which I switch to as the party of adventurers, for example, get set upon by a skittering mass of spiders the size of cartwheels...

The issue I have is the way I have to switch between playlists. My ideal would be to hit a button, a key etc and the currently playing song would crossfade into the next playlist, all smooth like... But what I get is an abrupt stop of the song as the other playlist drops in.

I'm using iTunes which is probably the least sophisticated music player on the material plane... I did play around with a script that I wrote that would fade one song before fading in the next which I assigned to a voiceover commander key which kinda worked, but still sounded a bit naff with the pause in between, plus there were issues with multi speaker setups on airplay.

Does anyone have any ideas of how to get the DJ like crossover so that one audio scene, let's call it, smoothly glides into the next over a few seconds.

I've looked at SyrinScape fantasy player, mostly with lust, but neither the IOS or Mac versions are in any way accessible, shame as it's an app specifically designed to simply hit a button and everything fades in for you with ambient sound and music all laced together in a beautiful way... Sigh...

Thoughts? Comments?

Thanks

O

@TheBlindDM