My name is Manuel Diewald and I am a Sydney-based guitar teacher in West Pennant Hills with a B.Mus. (Hons) (First) in Music Pedagogy from The University of New South Wales (UNSW).
Commonly on the guitar, whether you are playing a nylon, steel string, or electric guitar, you may find that the composer or original artist is playing a section of the music in a different position. To clarify, when I talk about playing in a certain position, for example, first position or fifth position, etc. that just means which fret your first finger on your LH lines up.
So why do we play in different positions? There are a couple of reasons as to why this is. Let's cover those now.
The first reason may be because as we play a note in a higher position, which means playing on the next lowest string, the tone of the note becomes warmer. Remember, the pitch is the same, it is the tone of the note that changes. This has to do with the lower string being a thicker gauge. Let's discuss this quickly.
A pair of D'Addario EJ46 strings string gauges are: Trebles .0285, .0327, .0410 Basses .030, .036, .044. From the first to the 3rd string you can see that the gauge, or thickness, of the string increases and then decreases slightly when beginning from the bass strings again though remember they are also wound with nickel. Let's take the note F in first position (1st fret, 1st string) and compare it to the same pitched F in 6th position (6th fret, 2nd string). The F in 1st position is going to sound slightly brighter than the F in 6th position due to the gauge of the string being thinner. You can see this in example A below.
Example A
The second reason may be to avoid a big jump or too many shifts in succession to get to higher notes on the fretboard. For example, you may be playing a melodic line that you have started in first position and need to end up in 7th position. Rather than having to shift too many times on the first string or have to jump quickly into the higher position, it may be easier to start off in 5th or even 7th position if possible to play that melodic line with more fluency. In example B below, there are three scenarios of the same melodic run. Bars 1 and 2 involve three different positions which means there are two shifts. Bars 3 and 4 involve two playing positions which means only one shift, and bars 5 and 6 involve only one playing position which means there is no need to shift during this melodic run at all, potentially making this the most ideal scenario. Remember though, the starting position of a melodic run can also depend on where you are playing before and after.
Example B
Try going through your pieces and seeing if you can either play a passage in a different position to get a warmer tone in your playing or to make a passage easier to play. You might be surprised how much easier you find a difficult section to play by changing the starting position of section.