This is the 3391st most frequent Japanese word.
歌い
"歌い" means "singing" in English.
In this sentence, '歌い' is the verb stem of '歌う' (to sing) and is used in combination with 'ながら' to indicate simultaneous actions.
彼は歌いながらギターを弾いています。
He is playing the guitar while singing.
Here, '歌い' functions as a noun derived from the verb '歌う', paired with '声' to mean the voice used for singing, indicating a quality.
彼女の歌い声は美しい。
Her singing voice is beautiful.
In this example, '歌い' is the stem of '歌う' combined with '始めた' to form a compound verb, indicating the commencement of singing.