Wait, WTF is this?
(Bear with me as I'm quite new to the concept as well and might miss something.) Basically, Walrus is a way to share music recommendations based on prompts. It's set up as a competition, and contestants will score points based on the quality and category-fit-strength of their submissions, but you don't have to view it as such if you would rather just think of it as a structured but fun outlet for exchanging tunes.
How it works: One person, the host/judge, decides on a set of categories (themes, concepts, technical specifications, whatever). The norm seems to be to have around 8-12 categories, and they can be anything from specifications such as "shorter than 3 minutes" or "cover songs", to silly criteria such as "has a color in the title" or "features an unusual instrument", to descriptions of vague conceptual feelings or aesthetics that may result in a variety of subjective interpretations. The host may provide sample tracks that would fit each category to give the players some frame of reference, and the host may also specify some of their particular tastes (potentially even banning artists or genres they particularly despise) but otherwise variety/uniqueness in genre is highly encouraged!
For some examples of categories and host guidelines check out these two that I have submitted to: Shad's (aesthetic-based categories with somewhat of a loose chronology/storyline) and KoC's (categories all based on titles of songs by one artist). To see a completed walrus game with the reveals of winners per category, skim through here or here.
Players will have some amount of time to select one track for each category and PM them to the host (for each one just send a simple URL for youtube, spotify, bandcamp, soundcloud, what have you). Submissions may be changed up until the deadline. Then the host will listen to each submission, preferably multiple times until they get a feel for the songs and can judge them fairly. Now, I don't think the following is strictly required but I got the idea from Shad and it sounds ideal: while listening through, the host should somehow set aside and randomize the links for each category such that they don't know which is whose until the reveal, so that there's no bias or preconceptions based on who submitted what.
Then, the host will score each submission according to how well it fits the category and much they like it overall, and reveal each submission publicly from worst to best. There is a Discord server in which the reveals happen live with the songs actually playing over audio chat -- I haven't witnessed this firsthand yet and am not entirely sure how it works or if we'll make use of it, or just post the links on the forum so people can follow along at their leisure. Depending on the host I think the whole process can take up to a month or two, with a couple weeks open for submission and then however much time the host needs to listen and sort through -- reveals can happen one category at a time, so the host may choose to reveal the scores for the first category before finishing listening to the later ones.
So, I hope that all makes sense (I recommend checking out the example links above). I'm going to go ahead and start one up in the next post so I hope there's enough interest.
Tagging some people who may be interested: