Nice job! My first thought is to NOT send Yale this link as a supplement. Although the quality is certainly very high, your guitar playing gets lost among the drums, keyboard, vocals, effects, mix etc. In addition, 5 people are credited writing the songs, so it's difficult to tell from the website what you wrote and what others contributed. So, I'm not sure how this supplement would enhance your overall application. On the other hand, it's very unique and makes you stand out.
Yale's music department is more classically focused and has specific requirements for musicians and vocalists submitting supplements: Yale Department of Music > Undergraduate Program > Supplementary Materials
"Submissions from instrumentalists and vocalists should consist of two or three pieces of contrasting styles ( e.g. Baroque, Classical, Romantic, Modern, etc.) which demonstrate abilities in the areas of tone, technique, and interpretation. Singers should submit at least one piece in a foreign language. Do not present selections from method books. Whole pieces or movements (as opposed to excerpts) are preferred."
Is there a way you could make an mp3 which included "Motions" but also followed Yale's directions to include two other contrasting pieces that featured you playing/singing in different styles? That might work better as an arts supplement and enhance your overall application than just submitting a link to your band's website.
If that's not possible, then I like Hunt's suggestion of including the link in the extracurricular activity list. It makes you stand out and that's good when there is so much competition! And the Admissions staff I think would enjoy it.