20 questions to test yourself on your Perfect Intervals! :)
View the full lesson at Diatonic Intervals: Perfect Worksheet | JustinGuitar
I know the perfect 5th from the scales, from the circle of 5th. The 5th from A is E and the 4th is D. Does it matter how I remember the perfect 4th? I go backwards. Like A is the 5th of D, so D is the perfect 4th. And with the flats I use MR CATO’S KEY SIGNATURE for the perfect 4th.
Hi @Rolandson
What you are describing in words is an exact match for reading the circle of 5ths clockwise (for 5ths) and anti-clockwise (for 4ths).
Hope that helps.
Cheers 
| Richard_close2u | JustinGuitar Official Guide
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Question answered later in the module!
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Extremely important thing to master
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“Let me know how you are doing in the discussion” is what I was trying to do. There was a problem saving my comment. I was using memorized 1,4,5’s but could have done better with the note circle. I am not familiar with topic revival and apologize if I’ve done it badly.
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Is it wrong if I call a note Aflat rather than G#, if so why. I mean If I said E maj scale contains E F# Aflat A B C# D# E would that be wrong, should I call the Aflat G#? Is it just a naming convention wrong or actually fundamentally wrong in some way?
Hi Tim @Timsters, I’m slowly working through Justin’s Practical Music Theory course. Here’s what I understand. First: it is custom to use each each of the seven note names once and only once when identifying notes in a scale. In your example, you’ve used A twice (Aflat and A). I don’t know if there is a reason for this other than it keeps things tidy. Second - and I also don’t understand why this is - I’m pretty sure we do not mix sharps and flats when identifying notes in a scale.
Usually someone in this wonderful Community who is smarter than me comes along to fill in the gaps in my understanding 
Stay tuned!
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@judi you have it correct Judi. Every Major and minor scale contain 1 and only 1 of each of the natural notes and Sharps and Flats never mix. Whether they are sharp or flat is determined by the scale degree to the Root note.
@Timsters in your example of the E maj scale using the W W H W W W H pattern of the major scale and using every letter once the not after F# has to be G#.
An easy why to figure out what the notes of a major scale is to write out the 7 note in order starting with the root and use the tone and semi tone pattern to put in the Sharp or Flats.
Justin has a lesson on scale degrees and interval in the PMT grade 3 of course.
(Edit to Clarify) Justin uses TTSTTTS not WWHWWWH sorry for any confusion
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Spot on @judi … though custom is not really a strong enough term. It is a requirement, a rule, a necessity.
Good question.
We do not mix sharps and flats because the major scale formula in combination with the rule concerning using letter names once only absolutely negates it as a possibility. It simply cannot happen. Even if we wanted to mix them, the process of writing any major scale means it will not.
Look at this outlandish example … the theoretically possible F## major scale.
Using the major scale formula: T → T → S → T → T → T → S
Using F## then letter names G, A, B, C, D, E respectively
Root note
This is found on fret 3 of the E string, two semitones higher than the note F.
F##
2nd scale degree
Move up one tone (now landing on fret 5 of the E string) and use the next alphabetic letter name of G. This is two semitones higher than the note G natural.
G##
3rd scale degree
Move up one tone (now landing on fret 7 of the E string) and use the next alphabetic letter name of A. This is two semitones higher than the note A.
A##
4th scale degree
Move up one semitone (now landing on fret 8 of the E string) and use the next alphabetic letter name of B. This is one semitone higher than the note B.
B#
5th scale degree
Move up two semitones (now landing on fret 10 of the E string) and use the next alphabetic letter name of C. This is two semitones higher than the note C.
C##
6th scale degree
Move up two semitones (now landing on fret 12 of the E string) and use the next alphabetic letter name of D. This is two semitones higher than the note D.
D##
7th scale degree
Move up two semitones (now landing on fret 14 of the E string) and use the next alphabetic letter name of E. This is two semitones higher than the note E.
E##
F## major sale = F##, G##, A##, B#, C##, D##, E##
I really wanted there to be a mix of flats and sharps but I was defeated by the constraints of the rules.
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Wow, that’s very cool. Thanks for the explanation and the great example, Richard @Richard_close2u !
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