just an idea to be getting on with.

I have seen this word used for both areas of art.

Could be an option if it is referring to music! What do the Kunstreisen involve? Is it visits to galleries and attendance at concerts? What countries?

I have and heard this term quite often

When you are not sure what a certain German phrase means, I would suggest that you look up its use in a real life context elsewhere, on the web, determine what exactly it means in German, then look for the English equivalent and determine when and how exactly it is used (for music, on music related web sites with content originally written in English. If you google for "sound worlds" on the web and in google books (a reliable corpus of the English language in print), you find that this phrase is indeed in use in music. Examples: "sound worlds to discover", "sound worlds in everyday space" etc. (It's interesting to see that in the context of sounds related to a specific place or characteristics of a place, "soundscape" is used: "The soundscapes of rural areas have changed radically over the past century". All examples given here are the result of a search in google books. When unsure whether a phrase is a "legitimate" English phrase, look up who the publisher is.
I hope this helps.

From Wikipedia: "A soundscape is a sound or combination of sounds that forms or arises from an immersive environment."

I recently translated a text for an artist who used the term 'Klangwelt' to describe a poetic world, in this case of light and shadow. Could it be something similar here?
Two suggestions that might fit in case this is what is meant..

Alyce Santoro, inventor of SONIC FABRIC, is an internationally noted conceptual and sound artist with a background in science and scientific illustration. She sees herself as a kind of archivist – a compulsive collector of snippets of the human auditory environment – who incorporates her specimens into her art.
http://www.designtex.com/audible_upholstery_Story.aspx?f=367...

Listening to Noise and Silence engages with the emerging practice of sound art and the concurrent development of a discourse and theory of sound. In this original and challenging work, Salomé Voegelin immerses the reader in concepts of listening to sound artwork and the everyday acoustic environment, establishing an aesthetics and philosophy of sound and promoting the notion of a sonic sensibility.
http://www.thewire.co.uk/shop/items/527/

Though I have to say that 'worlds of sound' is perfectly acceptable in many circumstances. What is not clear from the context you have given is the tenor of the text and its intended audience.

another option.