The single string guitar is basically what every newbie does when first picking up the guitar. Even though Deep Purples “Smoke one the Water” originally is played on two adjacent strings, it is a very good example of single string approach.
It is easy to play that tune on one string, and I think everybody is able to perform it after 5 minutes of instruction. Because of its simplicity, guitar-players often tend to skip exploring one-string playing further, and quickly move on to “proper” position playing. In my opinion, I think it is a loss, because position playing tends to make it harder for the player to understand the fretboard mechanics on the guitar. With single string guitar-playing, it is very easy to see how the melody is either ascending or descending.
The beginner will especially benefit from keep playing on one string, it is easier to play simple melodies, improvise etc. The more advanced player will benefit from this approach as well, there are a lot of different ways to explore this, like: figure out scales on all the strings, improvising on two strings, and moving chord forms around.
Below is a short clip of the e-blues scale played on the first string.
As you can see, this is very easy to do. You don’t have to mind fingerings, no worries about your right hand technique, you can just have fun with the scale and try to come up with your own melodies or improvisations:
For more inspiration, you may want to check out AC/DCs “Thunderstruck”. The entire intro is played on one string, and it sounds pretty cool right?
Single string guitar is a great way to approach the guitar, and is not inferior to position playing. It is just another way of approaching the guitar with a different mindset. I do of course play positions myself, and value them, but I think most players would benefit from challenging themselves playing on one string. It forces you to become more aware of the fingerboard mechanics, and the limitations challenge your creativity greatly.