Voice leading is the way each line gets from this chord to the next one. A choir does not sing a stack. Soprano, alto, tenor, and bass each have to believe their note is the next thing they would sing. If you only check that every beat is a consonant chord, you can still hand the alto a part that leaps a sixth, crosses the soprano, and has no idea where the phrase is going.
The standard taught in four-part chorale writing is still the right default for a church choir that wants independent parts. Keep a common tone when you can. Move the other voices by step. Let the bass take the leap that announces the harmony. Save contrary motion between the outer voices for the cadence, where the ear is paying attention. The parallel-fifths guide covers one specific failure of that default. This page is the motion around it.
Four lines, heard one at a time
Before you judge a chord, sing each part alone. A good alto line has a shape even with the other voices muted: mostly steps, a leap you can explain, and a resting place at the end of the phrase. If the alto is only correct when you hear the soprano, it is riding the chord, not leading a voice. Do the same for the tenor. Tenors get lost when their part is a series of chord tones with no neighbor and no repeated rhythmic motive. Give them a line they could hum in the car.
The soprano, when it has the melody, is already a line. Do not "improve" it with extra notes unless the arrangement called for a descant. The bass is the other real melody. It can leap, because leaps in the bass read as harmony: a fourth up into the dominant, a fifth down to the tonic, an octave when you need the root in a lower register. Even so, a bass that only alternates tonic and dominant becomes a drum. After the leap, let it step. A phrase of bass should be speakable.
Inner voices are where drafts go limp. When a generator, or a tired arranger, fills alto and tenor with the nearest chord tones, you get parts that look legal and feel like packing material. Ask of each inner note: did it hold from the previous chord, step, or leap for a reason? If the answer is "it was the leftover pitch," change it. Leftover pitches are how you get a tenor line nobody can memorize and a chord that is technically complete and musically anonymous.
Common tones first, then the smallest step
When two chords share a pitch, keep it in the same voice if you can. In C major, the I chord C-E-G and the IV chord F-A-C share the C. Let one voice hold that C. The other voices move by step or by a small skip to the new notes. The held tone is an anchor the choir can feel. If everybody leaves at once, the choir experiences a jump cut, and the pitch sags. This is the single habit that makes a hymn singable at sight.
If there is no common tone, prefer contrary or oblique motion between the outer voices, and stepwise motion in the inner voices. Oblique motion means one voice holds while the other moves. It is the cleanest way to change chord without asking two sections to leap toward each other. A passing tone on the offbeat can connect two chord tones a third apart. Put that passing tone on a weak beat, and make sure it resolves by step. A non-chord tone that lands on a strong beat and does not resolve is the defect the voice-leading check is built to flag. Do not call it color until it behaves like a suspension, a neighbor, or a passing tone.
A worked cadence in C major shows the habit. Soprano E-F-G-E-D-C. Bass C-A-B-C-G-C. The soprano steps down into the final tonic. The bass leaps down a fourth from C to G, then up a fourth home, which is the harmonic leap, and the inner voices can hold the common tone G from the dominant into the last beat only if you are not doubling badly. You do not need this exact line. You need the pattern: outer voices know where the phrase ends, inner voices do not jump to get there.
Leaps, tendency tones, and what has to resolve
A leap is a promise. After an ascending leap, the next move is usually a step down. After a descending leap, a step up. The ear accepts the leap because the line repairs it. Two leaps in the same direction, in an inner voice, feel like a yodel. The bass is allowed more of this, especially a fourth or a fifth that changes root, but even the bass should not leap twice and then leap again. If you need a large register change, do it once, at a barline, and then stay there for a phrase.
Tendency tones are the notes that already know their next step. In a major key the leading tone wants the tonic, especially when it is in the soprano. Ti to do is the cadence the choir expects. If the soprano holds the leading tone and then drops a third because you needed that pitch in the alto, the cadence sounds interrupted even when the bass went to the tonic. Resolve the soprano leading tone up. An inner-voice leading tone is still better resolved up when the section can hear it as ti. Falling to the fifth is a chorale shortcut you should use on purpose, not by accident.
The chordal seventh resolves down by step. If you add a seventh to the dominant, the voice that sings it has to step down into the tonic chord. You cannot hand the seventh to the tenor and then send the tenor up, hoping the alto will "cover" the resolution. The same voice resolves it. Suspensions work the same way: prepare the dissonance by holding it from the previous chord, sound it against the new bass, then step down. A suspension that appears from a leap is just a wrong note on a strong beat.
Spacing, crossing, and the frame of the outer voices
Keep adjacent upper voices within an octave. Soprano to alto, and alto to tenor, should not open into a tenth while the bass sits a twelfth below the tenor. The chord will sound like two duets. Tenor and bass may exceed an octave. That wider gap is normal, because the bass often needs the root an octave lower than the rest of the chord. When you check spacing, check the pairs, not the total span from bass to soprano.
Voice crossing is when the alto sings above the soprano, or the bass above the tenor, for a note that is not a brief ornamental neighbor. In simple SATB it confuses the section that just lost its place in the chord. A draft can look smooth on a piano reduction and still have the tenor above the alto for a beat. Sing the two parts. If you cannot tell who is who, the choir will not be able to tell either. The validator flags crossings for that reason. A crossed chord is not more advanced. It is usually a voice that should have stayed on its own side of the texture.
The outer voices are the frame. If soprano and bass move well, in a mix of contrary and oblique motion, the inner voices have somewhere to live. If soprano and bass both leap up a fourth, you have asked the whole choir to jump, and the inner voices will either follow in parallel or collide. Look at the soprano and bass as a two-part piece first. Then fit alto and tenor into the space between them. This is faster than fixing four parts at once, and it catches the cadence problems before they are dressed up with passing tones.
Cadences are where weak leading becomes obvious
At a cadence, reduce the motion. The penultimate chord and the final chord should be easy to sing from memory, because that is the spot the choir will rehearse ten times. Prefer stepwise soprano, a bass that states the root of the dominant and then the root of the tonic, and inner voices that move by step or hold. An authentic cadence does not need a new rhythmic idea. It needs clarity.
A plagal cadence, IV to I, is a color you can use under an amen or a quiet ending. The risk is parallel motion if soprano and bass both sit on a perfect interval and then both step the same way. Check that pair. A half cadence, stopping on the dominant, is useful at the midpoint of a stanza so the choir feels the phrase is not over. Do not end the whole hymn on a half cadence unless the text is a question you intend to leave open.
Deceptive motion, V to vi, is a one-time event. It works when the text refuses the ending the harmony promised. If you use it every stanza, it becomes the normal ending and loses the refusal. After a deceptive move, write a short path back to a real authentic cadence. Do not strand the choir on vi and call the piece finished. The singers will look up, because they can tell the tonic never arrived.
A review pass before anyone learns the part
Read the draft in this order. First the bass, to see if the roots and inversions tell the harmony. Then the soprano, to see if the melody still is the melody. Then alto alone, then tenor alone. Then each pair: soprano-bass, soprano-alto, alto-tenor, tenor-bass. The pair check is where parallel fifths, parallel octaves, and crossings show up. The dedicated guide on parallel fifths and octaves shows the interval test, including a twelfth that is still a fifth in kind. Do that test. Do not skip it because the chord symbols look familiar.
Then listen. Playback will reveal a line that is legal and still awkward: a repeated alto note under a moving text, a tenor leap into a vowel nobody can tune, a bass that arrives late because the leap is larger than you thought. CantuStudio shows a music report for parallels, crossings, range, and strong-beat notes outside the chord. The report is a list of things to fix. It is not a certificate. A bar can pass the report and still be a bad bar for your choir. Your ear outranks the report, and the report outranks a hope that rehearsal will smooth it over.
Change the file before you teach the bar. Export MIDI if a singer needs to loop one voice, PDF if someone needs paper, and MusicXML if you will keep editing in a notation program. MusicXML export is Pro. A free account does not download that file. The English pricing page is where the monthly limits are written down. The SATB arrangement app and the choir-director tool are where the draft is generated. The harmonization guide is the chord choice that this voice leading then has to connect. Use them in that order: chords, motion, parallels, then the rehearsal.