Band Hero

No Doubt -- Don't Speak

From missing 1 note, I'm pretty sure that the section of notes that must be hit 100% is in the solo.

The way i got this achievement was during my beginner vocals career run, i just played through the song Dont Speak by No Doubt (check the hint) and it popped up after i beat this song. Not to sure if this concept of playing vocals applies to all Secret Notes because im missing some in my vocals run which ill go back on other instruments

I can confirm that this must be done in "Don't Speak". I got 100% in "Just a Girl" first and did not get the achievement but I did get it once I got 100% in "Don't Speak".

The Hint is No Doubt, got this on 1st try of a No Doubt song, so this could very well unlock on Just a Girl as well. I did this on guitar where xxxPimizzlexxx mentioned he did it on vocals so at least those two instruments unlock it. I think you just have to play the song, not necessarily perfect. This song 'Don't Speak' is located in Everpop.

For this achievement you need to hit all the notes during a certain section of the song, it's obtainable on any instrument as each instrument has it's own section of notes for the achievement, you only need to do it on one instrument, the same thing goes for difficulty, each difficulty has it's own section of notes for the achievement and again, you only need to do it once on any difficulty to unlock the achievement.

Now the problem is that the sections are unmarked and no-one really knows for certain what or where the sections are, the best way to go for this is to try and complete the song without missing a single note, that will ensure you get the achievement, so play on a difficulty/instrument combination that you're able to full combo and you'll get the achievement.

Alternatively you could use the beginner vocals/mic fan exploit to get this and all the other achievements that are similar to this one, if you have a microphone/headset and a fan you can just leave the mic leaning against the fan while it's on and the game will register it as sound input and you'll be able full combo every song without actually doing anything.

Lastly, for this specific achievement you need to play; "No Doubt - Don't Speak", I've linked in a video below showing you the song and an expert/guitar FC, remember though, you don't need to play on this instrument or this difficulty setting.

* ^{Credit to bbforky for the video}

I played through on "I'm just a girl" and it didn't unlock, so it might not be in this song, though, saying that I missed two notes, one in the Second chorus "I'm just a girl......" and then again in the solo, after that chorus, so it is likely in one of those two if it is in this song.