For those who haven't grown up around choral music or in church, the term "SATB" might look like some strange code or an abbreviation for some government agency.
But all it means is: S=soprano A=alto T=tenor B=bass. In choral music there is a line of music for each part -- a line for the sopranos, a line of music for the altos, a line for the tenors, and a line for the basses.
The sopranos, of course, are the highest vocalists of the four, so their part usually is the melody -- the tune of the piece -- and is written in the treble clef. Right below the soprano line is the alto line, also in the treble clef, but lower than the soprano line.
In the bass clef the tenor part is on top, and the bass part on the bottom, in keeping with the vocal range of each type of singer.
If you look in a hymnbook (not the more contemporary chorus books) you will see there are 4 parts almost always all the way through the song. Those 4 parts are for the four vocal ranges we just mentioned: soprano, alto, tenor, and bass.
Piano players just starting out often play out of a hymn book just like it is written -- the trouble is, it was not written for a piano player, but for 4 different ranges of singers. That's why pianists need to learn what chord is represented by each stack of notes, from the bass up to the soprano, so they can then fill in and create a larger sound than they ever could just playing the singers parts.
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