Apex domains cannot have CNAME records.
Question and response
Question
dig sheetmusiconline.net. NS
Answer
sheetmusiconline.net. 4 NS ns2.sheetmusiconline.net.
sheetmusiconline.net. 4 NS ns1.sheetmusiconline.net.
Authority
The response has no authority records.
Additional
ns1.sheetmusiconline.net. 4 A 86.111.188.92
ns2.sheetmusiconline.net. 4 A 185.9.157.51
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0