HEY PIANO 4UHow a Synth Choir Works: Vowels, Formants and Ensemble
A real choir is many people, each shaping a note with their mouth. A synth choir imitates that with just three ideas: start with a buzzy sound, shape it into a vowel, and stack several slightly different copies. Once you know these three steps, every control on the choir panel makes sense.
Step 1: a buzzy starting sound
Your vocal cords make a buzz that is rich in harmonics, which are tones at whole-number multiples of the note you sing. A sawtooth wave is a simple electronic sound with the same property: it contains every harmonic, getting quieter as they go up. That makes it a good raw material, because there is plenty of sound for a filter to shape.
Step 2: formants turn the buzz into a vowel
The vowel you hear depends on the shape of your mouth and throat, which boost certain ranges of frequency. Those boosted ranges are called formants. Two or three of them are enough for the ear to recognise a vowel. A synth copies this with band-pass filters, which let a narrow range of frequencies through and quieten the rest.
| Vowel | Sounds like | Approximate formants (Hz) used here |
|---|---|---|
| Ah | “father” | 800, 1150, 2900 |
| Eh | “bed” | 400, 1700, 2600 |
| Ee | “see” | 300, 2300, 3000 |
| Oh | “go” | 400, 800, 2600 |
| Oo | “moon” | 300, 800, 2300 |
These numbers are typical values, not exact: real formants vary from singer to singer and with the pitch. Notice the pattern, though. Ee has a very high second formant, which is why it sounds bright. Oo and Oh keep their formants low, which is why they sound round and dark.
Step 3: many voices make an ensemble
One voice sounds like a solo singer. A choir sounds wider and softer because no two singers are exactly in tune or in time with each other. A synth copies this by playing several copies of the note at very slightly different pitches, a few hundredths of a semitone apart. The small differences make the sound beat and shimmer. In Hey Piano 4U the Voices control chooses one, three or five copies: Solo, Choir or Hall.
Attack, sustain and vibrato
Singers cannot start a note instantly; the sound swells in over a fraction of a second. Our choir notes fade in over about a tenth of a second and then hold at the same level for as long as you keep the key down, like the organ. Vibrato is a gentle, regular wobble in pitch, usually about five or six times a second. The Vibrato control offers Off, Light and Rich.
What it is not
The synth choir has no words, no breath and no consonants, and it is not a recording of people. It is an approximation made for practice. For real choral singing, nothing replaces listening to a real choir.
Practise with it
- Choose the Choir Warm-up tracks in the track list and sing along on a vowel as the notes light up.
- Try the same song on each vowel and notice how the colour changes.
- Play the Choir Chords tracks: each key press sounds four notes, bass, tenor, alto and soprano, just as the four voice parts of a choir would sing them.
- Play the game Name That Vowel to train your ear to hear formants.
The sound of a choir is built mostly from sustained notes, so it rewards the same skill as the organ: pressing cleanly and holding each key for its full length. See piano vs organ for how sustained and fading sounds differ.
Keep learning: Piano Scales for Beginners: Major and Minor, Fingering and Practice · How to Read Piano Notes: A Beginner’s Guide to the Staff