If you go up a P5th from D, which note do you land on?
It looks like you are asking about going up a Perfect 5th from D on the keyboard. From D, the tonic note, you will end up on the note A if you want a Perfect 5th chord.
Perfect 5ths are made up of seven half steps. So, if you follow on the keyboard, you will see a progression like this: D, D#, E, F, F#, G, G#, A. (# symbolizes sharp).
Also, here's an easier way to recognize perfect 5ths if you prefer not to count half steps. All fifths are perfect without sharps or flats unless you are referring to B and F. To get a perfect 5th here, you will need B and F sharp. The progression will look like this: B, C, C#, D, D#, E, F, F#. (To check, you can see that it's seven half steps from B to F sharp).
For notes with no sharps or flats:
1)From C to G is a perfect 5th.
2)From E to B is also a perfect 5th.
If both notes are sharped or flatted, they will still be Perfect 5ths. Try these:
1)From C sharp to G sharp ( C#, D, D#, E, F, F#, G, G#).
2)From A flat to E flat ( A flat, A, B flat, B, C, D flat, D, E flat).
Try other combinations if you like, but the principle still holds the same. Happy playing!
Your question refers to musical intervals, i.e., the distance between musical pitches. An interval, in music, is "the inclusive distance between one tone and another." A fifth is one of three musical intervals contained in a category known as Group I intervals. These intervals are structural in nature and can be modified in one of three basic ways: diminished, perfect, or augmented. The other intervals in this category are unison, fourth, and octave. The other category, Group II, contains the rest of the intervals: 2nd, 3rd, 6th, and 7th. These intervals can be modified in one of four basic ways: diminished, minor, major, or augmented. The interval to which you refer, P5, is the interval from do (1) up to sol (5) of a major scale and la (1) up to mi (5) of a minor scale. It is perfect because it, along with unison, 4th, and octave, is not affected by the mode of the scale. The intervals in Group II are indeed affected by the mode of the scale. However, as with most definitions in music, there are some exceptions. For example, do up to re and la up to ti are both M2; i.e., they are not affected by the mode.