Soundtracks
There are 13 official soundtracks in the main series of Kula Quest, with the first 10 being used for each world in the game, and an additional 3 tracks for bonus and hidden levels. However, there are multiple soundtracks that aren't included within the main series of the game.
Additional Soundtracks
Kula Quest Demo
The most well known removed soundtrack is from the first demo version of the game, KulaQuest. It can be easily found on various sites such as YouTube.
Track 14
A mysterious soundtrack has surfaced around the internet with unknown origins, and seems to have came directly from Twice a Man. The track doesn't officially have a name, and is ususally called "Hidden Track" and "Unknown Track". The track number located in the metadata of the MP3 conflicts as well, as 2 versions refer to this track to be #14, while another suggests it is #16.
For an unknown reason, one of the versions of the soundtrack (originally sent by Steve from the Discord server) contains the text, "Ripped By Rimo", suggesting that it was ripped directly from the game instead. Rimo is a very prominent person in video game music (VGM) ripping, who's website can be found here. They have ripped many soundtracks from Kula World, with each one containing the very same text in their metadata. Attempts to contact Rimo have been unsuccessful, as they have appeared to have left the VGM ripping scene altogether.
There is no evidence that suggests this track is hidden inside the game's files, unless it came from an unknown build of the game.
Misc
Soundtrack Playlist
A popular playlist containing the game's soundtracks used to exist on YouTube, with a thumbnail suggesting multiple unreleased soundtracks:
One version of the Track 14 contains the track number #16 as previously stated, so it could be a beta version of Arctic as noted in the graphic.
Email Response
The following is a response from an email sent directly to Twice a Man from Murphy regarding Track 14:
I made originally 14 tracks to Kula World and when I delivered them the programmers used them as they liked, i.e. I did not have control where which piece was to which "world". The piece you refer to has been in at least 2 different versions and was delivered to the game among the others tracks. There are also other pieces which have different versions. I sent some of the music to friends, included the piece you refer to and now you can hear all these tracks on Youtube etc.. It is out of my control. I hope some day be able to release the original music as an official audio release. I don´t know if you got wiser by this, but I hope so.
Best Wishes
Dan Söderqvist
Twice a Man
This response suggests that there are multiple versions of various soundtracks that have been created and put into the game, with the hidden track included in at least 2 different versions of the game. It is possible that this track could've been included in an unknown earlier build of the game at some point, and was ripped by Rimo.
Official Trailer
Inside the game's official trailer, the background music is a slight variantion of the Hills theme. It seems to be just a compressed and spliced version, and is unknown if it is actually different from the official version.