8 under clef and timing questions

Question

Please look at the below graphic, there are a few things that are confusing me:
1 - Why is there an 8 under the treble clef?

2 - This is in common 4/4 time, yet one of the beginning 8th notes (in each of the "bunch" of 4 notes) is actually a half note... which would throw the whole timing off for that bar... right?

Even when using Guitar Pro to put that in, if I put it in as a bunch of 8th notes it works, but if I try to put the first note as as a half and the rest 8ths it gives me an error :(

I mean the beams above say it's a group of 8 notes, but the "circle" in the note is not filled in which makes it a half note... right?

Answer 1

It's an octave clef. It's telling you all the notes written are actually down an octave. Since the guitar is already a transposing instrument where everything is transposed down an octave, it's essentially showing you the actual notes being played instead of the implied octave transposition. So for simplicity's sake you can just ignore it and play as you would with with a normal treble clef.

The lowest pitch a guitar can play in standard is E2 which is below the staff on the bass clef. Typically in guitar sheet music they notate this note on E3 so they can use the treble clef and it's just implied that the note is down an octave. With the octave clef, the note is actually an E2 even though it is written where E3 typically is because everything is down an octave.

You second question has is actually addressed in this question. Pretty much there are two ideas happening at once, the eigth note patterns and the whole note pattern that can be perceived as two different parts. Pretty much you would just play the half notes for the duration of the half note and play the eight notes while the whole note is sustained.

If they were two different parts, one would looks like this:

And another would look like this.

Since you are doing both, they become what you see in your score.

Answer 2

To answer the second question, you can use the "voices" feature of GP6 :

You can have 4 voices. Each voice has it's own "bar duration count" which is independent from the other.
To change the current voice, use the "1", "2", "3" and "4" buttons. When you'll add a note, it will be added to the currently selected voice.
The notes from the other voices are greyed.
The last button displays all the notes of all the voices, without greyed notes.

Here's how your example would look, depending on the voice selected and when the multi-voice option is on :

Answer 3

Adding to Dom's excellent answer, the tails on the dots are the clue. There's one set of notes with up tails, and one with down tails. Showing two parts to the line. Trouble is, it's a compromise, as it looks like the first note in the bar could be a minim with a tail AND a beam. Of course, this sort of note doesn't get used. It's written like that (and has been for centuries) for convenience, and I guess we've just got used to it!

I suppose, technically, the first quaver OUGHT to be written as a quaver rest, as the piece would sound exactly the same, but, why bother?