Genshin Impact: Use the conches to send the signal, The Lone Phantom Sail, Fontaine
So basically, you tap on your (element skill, not you basic attack)short note, and hold on your long note. Short note is only 1 tap, but long note you need to hold it for like 2 seconds, don't hold longer than that because you will fail.
It's like short/long/short/long/short/long/short/long/short/long. So it's 10 times.