For me, it is more complicated. When I listen to music, whether live, recorded, or broadcast, I tend to view the vocalist(s) as simply one of the various instruments — often a solo instrument, but not necessarily much more important than the others. Furthermore, I am increasingly convinced that the overall appeal and “sound” of any given piece of music depends more on the underlying chord structure than on the melody itself.

After voice, my formal musical training was piano and then trumpet, with guitar coming third among my main instruments. I perform most regularly on trumpet, in a brass quintet, a symphony orchestra, two brass bands and a variety of other groups. Incidentally, my favorite style for trumpet playing is jazz. My favorite style for guitar playing is folk.

While I am not sure about the proper musical term for this, one of my favorite things about the guitar is its irregularity. That is, due to the traditional tunings of the six strings, the chords used to accompany a song in the key of G sound completely different than the chords used to accompany a song in the key of A. On the piano or on the trumpet, I can play a song in either G or A, and the difference between the two keys will be mostly just the difference in pitch. On guitar, EVERYTHING changes — or, at least, in my humble opinion, everything SHOULD change. I have little respect for those guitarists who eschew open chords and instead focus mostly on bar chords, making the keys sound interchangeable.

When I listen to a recording of a piano or a trumpet, it is a relatively straightforward matter to roughly duplicate what I hear. With a guitar, it can be an incredible challenge discerning how the guitarist used the particular combination of fingers and strings to achieve the sounds — especially if the guitarist used a capo or non-standard tunings. Again, this is one of the things I love about the guitar, and, in my mind, what sets it apart from other instruments.

Incidentally, when I sing along with my guitar, I make extensive use of a capo to try and match the chords and fingerings of other guitarists, or simply to get the “sound” I am striving for, while suiting my own unique voice. I also accept that there are certain songs I simply cannot perform the way I would like to perform them, since even with a capo they fall outside of my vocal range.

I am not saying that a guitarist is obligated to copy the notes or keys of some other guitarist, although that is an option, and sometimes the best option. (Sometimes another instrument will attempt to duplicate the notes of a guitar riff — this is one way to handle performing a guitar-based song in a completely different key.) The guitarist is simply obligated to attempt to contribute to each unique piece of music using their unique abilities and the unique characteristics of the instrument — which they should embrace, rather than struggle against. Not every song is suited for every instrument or every instrumentalist or every vocalist, and there is no reason why they SHOULD be.

Finally, while I am not a music historian, it seems to me that “from the dawn of time” most early instruments capable of varied pitches tended to have a limited range and a limited number of available keys, so the vocalists would have to accommodate THEM. The development of instruments capable of easily performing in all keys came later …

Still, it all comes down to your definition of “song.”