I have a question concerning the intervals on a piano Between A flat and G, is it a Major 7th or Minor 7th? It seems both scales have the same note.
Intervals are not named for the major and minor scale, but the actual distance away from root note. Let's look at the typical intervals you would see with a root of A before we discuss what Ab would look like. Typically, when you talk about intervals with the root of A, you will have these notes:
A - Bb - B - C - C# - D - (D#/Eb)* - E - F - F# - G - G# - A
As you can see, we have 12 distinct notes and 7 distinct letter names. The distance away from the root in combination of the letter name of the note gives us the interval we want. In this case, we would treat the letter names the following way:
A - 1st/8th B - 2nd C - 3rd D - 4th E - 5th F - 6th G - 7th
Now as you can see, some of the groups that have two distinct notes for each letter which are B, C, F, and G. The smaller of these intervals will be minor and the bigger ones will be major. The other interval are perfect, but can also be raised to become augmented or lowered to be diminished with the exception of the 1st which can only be augmented.
Applying this to the notes we used above we get:
A - P1 Bb - m2 B - M2 C - m3 C# - M3 D - P4 (D#/Eb)* - A4/d5 E - P5 F - m6 F# - M6 G - m7 G# - M7 A - P8
Now we'll turn our attention back to what Ab to G would be. It's the exact same logic, but all notes are lowered by one and you'll see:
Ab - P1 Bbb - m2 Bb - M2 Cb - m3 C - M3 Db - P4 (D/Ebb)* - A4/d5 Eb - P5 Fb - m6 F - M6 Gb - m7 G - M7 Ab - P8
So with this, you can easily see that Ab to G is a Major 7th.
* The D#/Eb is known as the tritone and can be considered either a 5th or a 4th depending on what you are doing.
G is eleven semitones higher than A-flat, so it's a major seventh interval.
(See the 'Main intervals' table here - https://en.wikipedia.org/wiki/Interval_(music) )
You are confusing the terms major and minor slightly. The interval is indeed a major 7th, but maybe you feel that in the melodic and harmonic minors, also, that interval features. When the interval goes from (in your example) Ab to G, that is known as a major 7th. It's one semitone larger than a minor 7th. The minor 7th is actually found in the natural minor scale of Ab minor as a minor 7th, going from Ab to Gb.