Quoting Commentary for I Chronicles 13:13

The number of Levites (of whom Scripture tells specifically as singing hymns) is eight. They were: אסף, הימן, ידותן ,איתן האזרחי,; this makes four. Add Levi, who is referred to here as בן “son;” this makes five; then there is the one called על הגיתית, a reference to the family of Gattit a song offered by that family who hosted the Holy Ark. (compare Chronicles I 13,13). This gives us six. Add the sons of Korach; this makes seven. Finally, there are the “sons” of Moses giving us a grand total of eight such “singers,” or better: “composers of songs and hymns” who were all Levites. These eight people between them used eight musical instruments. The instruments are known as:
1) נגינות (Psalms. 4,1).
2) מחלת, (Psalms. 53,1).
3) עלמות שיר (Psalms. 46,1).
4) משאת (Chronicles I 15,22).
5) נחילות (Psalms .5,1).
6) שושנים, (Psalms. 45,1).
7) גתית, (Psalms. 8,1).
8) שמינית, (Psalms 6,1).