In the second bar, there is a high E and low C to be played together. If you need to play this on a guitar with a plectrum, how do you do it?
First of all, this is not intended to be played with a plectrum. But if you really want to use a plectrum here, you would use hybrid picking, i.e., pick the low C with the plectrum and use your middle finger or ring finger to pick the high e string.
Being really smartass, the simple way is to fret the A string on 3rd fret, making the C, and use another finger on the bottom string over the 5th fret, to make the high E as a harmonic. Then you use the pick to pluck the two bottom strings.
Would I (or anyone) do it like that? Most likely not! But the question was asked, and that's a simple answer!
Most players would use thumb and finger, pick and finger, or two fingers, or mute the strings in between. But purely using a pick, that's the way to do it!!!
To play this solely with a pick, you have limited options:
- Finger the 3rd fret of the A string (middle C) with your first finger and the 5th fret of the B string (E) with your third or fourth finger (depends on hand size). You need to use the rest of your index finger and/or the in-between finger(s) to lay more or less flat on the D and G strings to mute them. Whether you do this with one or multiple fingers is a matter of preference and comfort.
My hands are smallish so I would use first and fourth finger to fret the notes with the remainder of my first finger laying on the D and G strings.
- Same as above but fret the 8th fret of the low E and the 9th fret of the G. Mute the A and D strings as above.
In both examples, you'll have to use an abbreviated and controlled strum motion that starts on the lower of the two fretted strings and ends on the higher. The first example above is possibly a more desirable voicing in the context of the rest of the piece (judging only by the previous measure). The second example is possibly easier to play because the beginning of the strum is on the lowest string and can be more forgiving of your precision.
(As an aside, for a melodic line like this I would personally use the pick for the lower note and my third finger to pluck the higher note without needing to mute anything. Both techniques are worthwhile to learn.)
In addition to all the suggestions so far, applying an alternate tuning is another option. Though I would not provide a tuning in the answer without seeing the entire sheet as a tuning that makes this one pair easy to play might ruin the play-ability of the rest of the tune.
The best Plectrum only approach would be (as has been suggested) to play this as a bar chord in 3rd position with the D and G strings muted with the left hand fingers.
By the way, the solution to this one pair should make the other parts too difficult to play. The bar before it has a C-G-e and this is 1-5-3(8va) of the C chord. The A-form in 3rd position would allow you to play both of these bars without shifting position. If you are not completely restricted to a plectrum only solution then grabbing that part with "hybrid picking" works (as has been suggested in an other answer).