During the F Maj scale Justin mentions you can’t have A and A#, I was wondering if I missed something in a previous lesson or what the reason for this is, It best practice to call it the flat equivalent in these cases? Thanks!
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You can only use each letter in a scale once. So in this case the notes would be
F G A Bb C D E not. A A#
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Hi all
It would be right naming the Notes out loud while playing the scale downwards with the according Flats right? So for example Playing the A Scale up: A-B-C#-D-E-F#-G#-A and then Down A-Ab-Gb-E-D-Db-B-A 
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@Domi79
That is a perfectly logical thought to have, and an interesting question to ask.
The short is answer, however, is a clear and unambiguous no.
The A major scale is the A major scale and nothing but the A major scale. It does not matter if you play every note in sequence ascending in pitch, descending in pitch, with jumps from the first note up to the 5th note, down to the 2nd note, up to the 7th note, down to the 4th note … or whatever random pattern of interval jumps you could make … the notes stay the same.
There is some sense to say that the note one semitone higher than A is A# and to then suppose that the act of moving up in pitch is equivalent to making a note take a # (sharping a note - if we can use # as a verb).
Equally, there is some sense to say that the note one semitone lower than B is B♭ and to then suppose that the act of moving down in pitch is equivalent to making a note take a ♭ (flattening a note - if we can use ♭ as a verb).
And so far, we are not causing ourselves any problems. Because the note we land on when ascending from A and when descending from B is the same note. It has been given two names. This is when we need to use the phrase ‘enharmonic equivalent’.
BUT
The symbols # and ♭ are not indicators of direction (ascending or descending). They are not verbs. They are descriptors of something absolute.
The A major scale, shown as a full octave, is A, B, C#, D, E, F#, G#, A.
The note G# can not be rewritten as the note A♭.
The note F# can not be rewritten as the note G♭.
The note C# can not be rewritten as the note D♭.
That would lead to a major scale that breaks the fundamental rule:
Each letter name must be used once and once only whilst following the W-W-H-W-W-W-H formula which is taught in the Major Scale Theory lesson just before this one.
Does that help make sense of it?
Richard 
Hi Richard
Thank you for the Feedback 
Makes perfect sense now that you explained it. I forgot the fundamental rule that each letter name can be used just once according to the Formula. So I understand that in any Scale the Name of the notes in the Scale are Always the same and absolute, no matter of the direction you play them.
But then outside of the Scales, if I play for example a Solo or a Melody one one starting from the 12th Fret of the A String and move downward the Neck and the last Note would be lets say Bb, then I would name all the Notes in the melody (where there are notes with Flats) as Flats, where I to communicate with an other Musician right? 
Dominic
The starting note is not important.
What matters above all else is the key.
The key of the music and how that informs the notes / scale(s) you choose to play the solo or melody over.
Melodies do tend to both move up and down, ascending and descending, as a matter of course. Very few melodies only move in one direction away from the starting note.
That movement, on a guitar, can be laterally up and down a single string, or across strings.
Given that you have said the melody descends, this could be 5th string fret 1 or 6th string fret 6 (same note at two different locations on the guitar).
I am going to assume that your music is in the key of A major, given that is the scale you were asking about.
A, B, C#, D, E, F#, G#
Because music theory guides us, in many circumstances, to only use one type of accidental and not to mix them, we should not really call any note in the key of A using the symbol ♭ symbol as it is a key that necessitates using the # accidental to name its scale degrees. That said, the note you have asked about, which is not a scale tone but sits midway between the root note and the 2nd scale degree, would usually be called the ♭2 - in other words B♭. That is the convention for the note you have selected.
This is where things can become less clear cut. It depends. If you played the note one semitone above B and one semitone below C# it would be called the ♭3, the minor 3rd, the note C. If you played the note one semitone above D and one semitone below E it could take on two names. It could be called the #4 or it could be called the ♭5. The name #4 would be used if context required alluding to a ‘Lydian’ modal sound. The name ♭5 would be used in a blues-jazz type of setting.
You are stepping somewhat off-piste in terms of the PMT course and lessons but these are good questions and interesting paths to eventually explore.
Richard
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OK I think the whole Key topic is coming up in the next lesson I think this will make a lot of stuff clearer for me But I keep in mind for now that the Key is …The Key (the Name makes some sense in this regard) and matters the most.
Thanks for the help, much appreciated 
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