Do you see the difference?
You will be able to see the difference with some open strings. (The red letters found on the picture)
Let’s find out the harmonizable notes among the chords.
But before that, there is something important you should know.
This picture shows practical notes but we have to use the next picture whenever we need to find out the harmonizable notes among the chords on the fingerboard of your guitar.
As you can see, these notes are different from the picture.
We are going to skip this explanation because we will learn the reason later.
You may want to print it out and put it where you can easily reference it because it’s worth having for future use.（It’s in the Qactus Starters Manual as well）
Musical scores are not necessary for players who have a goal to play the guitar and sing while following chords. It’s also one of the reasons why the guitar is loved by a lot of people.
There are many websites which show the lyrics and chords of a song but it will be better for the person learning to play if they had a function to change the key. QactusCore has a function like this. QactusCore changes the key the guitar is in, making it easier for the beginners to learn to play.
Make sure you change the key in the website of the lyrics & chords into 「-2」 if Qactus is inserted on 「2nd fret」
The chords on the Qactus setting will be different from the original version of the song but you can play the guitar along with the original music track (or video) if you follow the directions (both will be the same key).
Allow me to repeat it.
The key you normally play the guitar in without Qactus is different when you play the guitar with Qactus.
Never mind if you are confused. It’s ok. You don’t have to think anymore. This page will try to help you out.
Confirm that it should be 「-2」 on this website (lyrics & chords) as we have read earlier.
We are going to divide some chords into [the three rooms -- Yellow, Red and Gray] the way you have already learned. We can get started once you are finished dividing the chords.
It will be hard if we only have three options for notes, however, remember the Gray Room, it gives us more options for finding harmonizing notes that will help to lessen the burden on beginners.
Actually, all the options (notes) in the Gray Room are allowed to be added even if it’s vacant, as long as the notes harmonize well with the chord you are trying to make. The Red Room is not as flexible and does not work like the Gray Room.
If you can’t seem to find any notes in the Yellow Room and Red Room, you can see if these options (notes) in the Gray Room sound cool and harmonize. Sometimes these options (notes) in the Gray Room are practical and can help you find notes to harmonize.
However, you should be careful when choosing notes from the Gray Room because there are some notes that will not harmonize well with your chord. Generally, 7 and M7 are good choices and work with many chord groups.
Often, if the Red Room has [m ] in it and there is a  in the Gray Room the two will harmonize with your chord. Try it and see but listen carefully for the harmonizing notes. Sometimes these notes do not work well together. You will be able to hear it if you are listening carefully.
By the way,  or [M7] in the Gray Room will often harmonize if both the Red Room and the Gray Room are vacant. Try and choose the notes that feel the most comfortable because there are only three options , [M7] or none.
Depending on the situation, it may be possible for you to try the additional notes in the Gray Room but only when the Red Room is vacant. There are notes that can change the way a chord sounds and may be incorrect for the chord formation. Please listen for the harmony between the notes. Also, bear in mind that some open strings are also notes that will harmonize in a chord.
If you choose the correct options (notes) in the Gray Room then you will have more options of notes that will harmonize in your chord. Also, you will have more possibilities to leave open strings in your chord formations. Always remember to judge with your ears and listen carefully.
You can download and refer to the sheet to avoid forgetting the positions.
QactusCore Note-1［pdf file］
We have another sheet for Qactus on 2nd fret.
QactusCore Note-2［pdf file］
Please refer to QactusCore when Qactus inserted on different fret.
You can adjust the key if you use a capotasto and Qactus.
For example :
However, Qactus may not work properly if it is place above the 9th fret.
There is no need to try such a rare setting now. We still have a lot of things to learn.