To show dance in your message, you just need to add to the usual kaomoji symbols symbolizing notes or depict dancing movements by using slashes of different directions.

Music and dance
ヾ(´〇`)ノ♪♪♪(〜 ̄▽ ̄)〜〜( ̄▽ ̄〜)
ヽ(o´∀`)ノ♪♬(ノ≧∀≦)ノ♪ヽ(^^ヽ)♪
♪(/_ _ )/♪└(^^)┐( ̄▽ ̄)/♫•¨•.¸¸♪
└( ̄- ̄└))((┘ ̄ω ̄)┘√( ̄‥ ̄√)
~(˘▽˘)~(〜 ̄△ ̄)〜(「• ω •)「
(^_^♪)⁽⁽◝( • ω • )◜⁾⁾( ̄▽ ̄)/♫•¨•.¸¸♪
(〜 ̄△ ̄)〜ヘ( ̄ω ̄ヘ)ヾ(⌐■_■)ノ♪