What is the meaning of イ?

The katakana syllable イ (i). Its equivalent in hiragana is い (i). It is the second syllable in the gojūon order; its position is ア行イ段 (a-gyō i-dan, “row a, section i”).

la (musical note)

A transliteration of the Korean surname 이(李) (I), Yi; or of 리(李) (Ri), Lee