Those are actually some very good observations!
In regards to the scale from G going down to G (at 19 to 22 seconds in the lesson):
Is it normal when doing scales (that you are not used to) for it to be harder going back down the scale than it is to go up?
Yes, it's a very common issue!
Don't worry, with time and practice it will get better, just try to do runs downward more often.
I am using the metronome & have got my speed up to 135 bpm for that scale (playing every other note on the beat). Since the main tempo is 85 bpm, I assume I have to get my speed up to 170 bpm (again, playing every other note on the beat) to be at tempo, correct?
This question concerns note durations and some simple mathematics!
- Time signature of the lesson is 4/4 which means there are 4 quarter notes within a bar.
- Your metronome ticks 4 quarters
- When you play 135bpm, and you play every other note, you play eight notes @ 135bpm
- If you want to play sixteen notes (which are the half value of eight notes) @ 85, then YES - you need to be able to play eight notes @ 85x2= 170bpm
Your method of practicing is very good, because you are on slower tempos, simply by using eight notes instead of sixteen ones, which will give you more low tempo range (hope it makes sense!)
I am going to try a theory question here, is this particular scale a mixolydian scale?
Mixolydian scale (or Mixolydian mode) is the scale that builds on V degree of major scale. We are in the key of C major, and V degree of C major scale is G. This note builds G mixolydian scale. G mixolydian is not that different from G major scale, it only has flatted 7th note.
By going G - E - F - D - E - C ... etc., is this what is meant by the term, "intervals"?
Intervals are spaces between the notes, they can be whole step and half step. Here is example of displaying intervals:
G - A - B = C - D - E = F - G
symbol "-" is whole step, and symbol "=" is half step. Whole step is distance of two frets on the neck, and half step is distance of one fret (two frets next to each other) on the neck. If you check out piano keys for example, you will quickly notice where there are half steps (there are no black keys in between white ones there!)