Harmonies

In music, if you look at the melody line and see it as a horizontal line (from start to end), then the harmonies can be seen as going vertically, adding the the piece of the music as opposed to lengthening it (Jamini, 2005, p.147).
If you listen to any song, you'll be able to hear harmonies (whether it from a solo artist where they sing on top of their lines when recording or even in more common choirs and acapella groups where the sound is intensified by the union of voices all singing slightly different notes).

In popular music, chords are known by their "root" notes then any another characteristics (such as sharps and flats).
When creating a harmony, the easiest way to do it is by using a chord as the foundation (for example "C major").
C major is made up up of its root note (C), the 'third' note above (E), then the 'fifth' above the root (G), creating a C major triad. Creating a harmony based on C major is as easy as someone playing/singing each note on top of the chord. You can also 'stack' on what you already have, with the "seventh" note above the root (which in this case would be B), which creates almost dissonance.

When performing live, it's hard to create a harmonies when you're on your own unless you have a backing track or a loop pedal however for me, it's not something that I'm going to be doing.
I was inspired however when I was listening to a live performance that Ed Sheeran did where he got the audience to participate and sing along with him

He tells the audience to sing along to the bit in the chorus and explains before he starts the song, what they're singing.
Although he doesn't necessarily do anything harmony wise with the audience, it helped me to figure out a way I could create a harmony in a solo performance when not using a backtrack/pedal.

Using people in the audience would not only help to make the piece sound more pleasing to the hear, but also a performer, it's important to connect with the audience through stage presence and body language.

I've been looking at how to incorporate it as part of my piece and as I'm doing a narrative style song, it makes it tricky at what I am able to do, as it has to simple enough for people to pick up on the spot. Also, it makes it musically challenging as I have to be able to correct things if people don't sing the right notes halfway through so I'd have to adapt on the spot (however I find that improvisation comes naturally to me)

(Pro Tools does come in handy sometimes)