Combining Notes to Play Harmony on a Piano
To play harmony on a piano, you have to play two or more notes, some interval apart, at the same time. Try playing the notes of each interval — perfect, diminished, augmented, major, and minor — as shown in the following figure at the same time.

Playing intervals all together now.
They sound perfectly lovely, but how do you use these intervals to create harmony? You can
Notice that the notes in each interval are stacked. When two notes appear stacked, or attached to the same stem, you play them at the same time. You know, in harmony.
You don’t have to figure out how or when to add intervals to a melody. The composer does that for you and notates these intervals in the printed music you play. But you should understand that all these intervals combine with the melody to make a very harmonic tune. Sure, you could just play the melody by playing only the top note of each group of notes, but your audience will appreciate the extra effort of playing the intervals. Besides, why do you think you have so many fingers?
Of course, if you want to add intervals to a melody yourself, try choosing the interval either a third below or a sixth below the melody note. And, one of the easiest ways to do that is to play single notes with the left hand that form intervals when combined with the right-hand melody notes. Often, you simply play one note with the left hand and hold it for several measures as you continue with the melody. However, you can fill out the sound even more by adding a harmonic interval to the left-hand part.
To give a song a little more movement, you can play a harmony part in the left hand that matches the melody note-for-note. Or go for four-part style with simple intervals in both hands. Just a couple of notes create a nice, full sound:

A full, choir-like harmonic treatment.

Piano Glossary
accidental
A sharp or flat not in the key signature.

Piano Glossary
bar line
A line that divides music into measures, breaking up the musical paragraph into smaller, measurable groups of notes and rests.

Piano Glossary
bass clef
A musical symbol that indicates lower the notes, generally played with the left hand.

Piano Glossary
beat
The steady pulse of a piece of music; what you tap your foot to.

Piano Glossary
C position
Placing your right-hand thumb on middle C and your other right-hand fingers on the four successive white keys.

Piano Glossary
chord
Three or more notes played at the same time.

Piano Glossary
Circle of Fifths
An order that starts with no sharps and flats and cycles the ring of keys to all 12 keys.

Piano Glossary
clef
A musical symbol that tells you the names of the lines and spaces on the staff.

Piano Glossary
fingerings
Numbers written above the notes that tell you which finger to use for each note.

Piano Glossary
G position
Placing your right hand on the G above middle C and your other right-hand fingers on the four successive white keys.

Piano Glossary
grand piano
The largest piano. A concert grand is 9 feet long; a baby grand is about 5 feet.

Piano Glossary
grand staff
The treble clef and bass clef joined together with a brace at the start of the left side.

Piano Glossary
home note
The base note of a piece of music. All the notes in a song have a relation to the home note based on how close or far they are to home.

Piano Glossary
interval
The distance between any two musical notes.

Piano Glossary
key
A set of notes that corresponds to a certain scale.

Piano Glossary
key signature
Notation placed just after the clef on every line of music to tell the performer what key the song is in.

Piano Glossary
ledger line
An imaginary line running above or below the staff, extending the five-line staff to represent notes above and below the staff.

Piano Glossary
measure or bar
A batch of notes with a specific number of beats — most commonly four beats — that helps a performer keep time.

Piano Glossary
middle C
The 40th key of a piano, close to the center of the keyboard. The first key a new pianist learns the placement of.

Piano Glossary
MIDI Musical Instrument Digital Interface
A device that allows communication between electronic, digital equipment.

Piano Glossary
notehead
The printed representation of a note. A notehead is oval and may be solid or open, an attached to a stem or not.

Piano Glossary
octave line or ottava line
The line that tells you to play the indicated note or notes an octave higher or lower than written.

Piano Glossary
root note
The lowest note of a chord.

Piano Glossary
scale
A series of notes in a specific, consecutive order.

Piano Glossary
staff
The five lines and four spaces music is written on.

Piano Glossary
tempo
How fast or slow the beat is.

Piano Glossary
time signature
The indication of the meter of a piece of music.

Piano Glossary
tonic
The bottom note of a scale.

Piano Glossary
treble clef
A musical symbol that indicates higher the notes, generally played with the right hand.

Piano Glossary
triplet
Three notes per beat.

Piano Glossary
upright piano
A piano that sits upright against a wall. Also called verticals, they vary in height from the spinet up to full-size uprights.