The main thing about choir parts is to play triads. Major triads are THE MOST POPULAR, and then minor triads. Diminished are less popular, as are sus chords. Dominant chords with extensions are extremely hard to do, and you wont see these unless you're transcribing parts from some really advanced choir, or Take 6. See VT about those.
I should also mention the concept of knowing all your diatonic triads. Diatonic means from the key.
So if you're in E, its a triad built off of every note in the E major scale. A Triad is just 3 notes where each is a 3rd apart. either major 3rd or minor 3rd. In E, there are 4 sharps, (F#, C#, G#, D#)
EG#B, F#AC#, G#BD#, AC#E, BD#F#, C#EG#, D#F#A
(play them through a few times and get um under your fingers .)
Listen to a song from beginning to end a few times, and Identify which parts of the song are strictly unison, and which might sound like you have another part at the same time. Most often, songs will have a ton of unison sections, and just a few parts. Probably more songs have more harmony, and a little unison. And some have an even mix.
Now Koda was right on it when she said, find out which part has the melody. Said another way......Who is leading the song? Israel, Fred Hammond, Norman Hutchins, Tonex?!!!! lol
If you know that persons voice, thats half the battle. Israel is an alto. In his songs, if he is leading them, look for the Alto to have the melody, remember they said that in Delaware.
Learn the melody
Learn the melody
Learn the melody
Your parts, for the most part will be major triads, especially when you're in a major key. So try a major triad that fits the key you're in, and the music. Listen to the original and check yourself. If you can play the melody with triads, thats what your choir or praise team will be doing. Spend your time only on harmony sections. Like if you start teaching the song, teach that first. So learn that part first. Its human tendency to sing with the lead/melody, so if they know the song, thats the part they'll learn easiest.
If you dont have the parts yet, listen some more, and see if you can hear clearly another note above or below the melody. If you heard it from a voice, its probably correct. add it to the melody together, and see what triad goes with those two notes.
So you're in E. You have heard a C# and an E. Then by theory of knowing all your diatonic chords in the key of E major, you know the missing note is an A, as in Amajor. AC#E. Now you have an A triad in the voices, doesnt mean you will have the bass guitar hanging on an A, while you play the chord. Your right hand is now playing the melody. That includes the main chords, and PASSING chords, or chords in between two main chords.
*****Notice***** with a C# and an E sounding in the voices, you could have said it was a G# for the last note. BBBBUUUUUUUTTTT, that would be a minor triad. Only explore minor triads after you've tried the obvious major choice, first. Unless you just hear it, of course, like VT.
You're still in E. You have heard a F# and a D#. Then from knowing those diatonic chords, and knowing you are supposed to try major triads first, then you know the last note is probably a B. BD#F#. If you would have chosen A as your last note, as in D#F#A, that'd be diminished which isnt very popular. Its that easy. And remember, these are voices. So you're movements will likely be small movements, so theres good voice leading to the next note for almost everybody. If theres a big movement down or up, it will likely be an inversion.
Go listen to a choir song, you know. Come back with questions. Time for me to get ready for work. Also if you can remind me, cause I rarely come here. I was just doing a search