Although a notehead usually indicates a pitch by it's position on the staff, different types of noteheads may also indicate a certain technique or instrument.
A normal notehead imposes no special technique and is played naturally.
Figure 1: Five notes with normal noteheads.
A cross notehead may indicate a note of uncertain pitch, usually for unpitched percussion. It may also indicate a muted note.
Figure 2: Five notes with cross noteheads.
A diamond notehead usually indicates a note that is fingered but not played, such as a string harmonic. It may also indicate a piano key depressed silently.
For guitar harmonics, diamond noteheads a crotchet or shorter are written with the diamond filled-in.
Figure 3: Eight notes with diamond noteheads, some with filled-in diamonds.
A beat note is written as a slash and indicates the rhythm of chord symbols. It is up to the interpreter to improvise the voicing of each chord played.
There are two species of beat notes, ones with a stem and one without.
They are usually written only on the middle line of the staff.
Figure 4: Six beat notes, some with a stem and some without.
A headless note indicates purely a rhythm in contemporary music, either because a previous note or chord is being repeated, or because, like the cross notehead, the pitch is indefinite or improvised.
Headless semibreves are hard to read.
Figure 5: Five headless notes with the semibreve being invisible.
Stemless notes are useful for arrhythmic music such as plainchant.
Figure 6: Two stemless notes.
Cue-size notes are used to mix normal-sized and cue-sized notes within the same chord.
Figure 7: Five cue-size notes.
A notehead with a slash indicates a rim-shot in percussion notation.
A slash or backslash may be used.
Figure 8: Five notes with slashed noteheads.
Arrow Down Notehead
An arrow down notehead indicates an extremely low unspecified note. These notes are written without a ledger line.
Figure 9: Five notes with arrow down noteheads.
Arrow Up Notehead
An arrow up notehead indicates an extremely high unspecified note. These notes are written without a ledger line.
Figure 10: Five notes with arrow up noteheads.
Shape notes are used for shape note notation (also "sacred harp" music), in which each notes indicates a degree of the given scale.
Figure 11: The C Major scale in shape note notation.
Large Cross Notehead
A large cross note is used in marching percussion, generally indicating all drums play in unison.
Figure 12: Two large cross notes.
A ping notehead is used in percussion notation which indicates a specific type of rim-shot.
Figure 13: Five notes with ping noteheads.
Also see Notes | Dynamics.