Here's the first ever post on vocals, hope to see more in the future. If you're not too interested in vocals, do check out the video, because its nevertheless an enjoyable listen. Will put vocals under the 'others' section for now...
So what exactly is harmony? Well, basically, harmony is anything that accompanies the melody. Often, the harmony can occur as chords, which are simply a few notes played simultaneously. Harmony can also occur as broken chords, which are the same notes in the chord, only they are played one after another. Often, listeners do not even know they are hearing harmony because the composer hides it so well from them. In almost all cases, though, the harmony that is being played can be converted into a chord.
The major triad is one of the most basic harmonies in music. It is formed by taking the first, third, and fifth note of the major scale and playing them simultaneously. This triad has a "happy" sound to it and is often used as the basic chord in a major piece. So what's the big deal with triads? Well, they are a very common form of harmony. By themselves, though, they don't mean too much. This is because music uses a wide variety of chords that have complex relationships to each other. Let's make up an example so that we understand this section better. Let's say we have a piece in the key of C Major. This means that many of the melodic notes are taken from the C Major scale. The basic harmonic chord also starts on the key of C (the notes would then be C, E, and G). Now this doesn't prohibit the composer from using other triads starting on other notes in the scale. For example, the composer can use a triad starting on G (the notes would then be G, B, and D).
How does this relate to vocal harmony? Very simple. When the melody singer is singing the C note, then the alto sings E and the tenor singer sings G. Whenever the melody singer changes their note, then the tenor and alto change accordingly. Its simple but takes lots of practice. You can also stray away from the alto and tenor to form different harmonies. This is especially effective in worship when you consider dynamics and progressions. The key is to be sensitive in worship. This applies to both instruments and vocals. It’s not about being noticed, but to create an atmosphere of worship.