The "greater than" sign is diminution, also written as dim (diminuendo).

The "less than" sign is a crescendo, also written as cresc (crescendo).

Crescendo and diminution symbols are commonly used intensity symbols, which are used to represent the process of increasing or decreasing the volume respectively.

The crescendo symbol consists of two lines of equal length, connected at their left ends and gradually opening out at their right ends. This symbol begins with a note using the crescendo symbol, with the open end drawn to where the composer wanted the effect to stop. The crescendo symbol is drawn exactly the opposite of the crescendo symbol, with the intersection on the right and the opening on the left.

Extended information

The sound produced by changes in intensity can express strong emotions such as angry cries, violent storms, majestic and tragic, galloping and unrestrained, courageous and strong, and can also express low voices. Confide, murmur, comfort and caress, sigh and sob, sweet happiness and other subtle inner feelings.

It can also express the wonders and beauty of nature such as the echo of empty valleys, the ringing of bells at dusk, mountain water, gurgling creeks, and even visible and intangible objects such as sunlight, moonlight, clouds, and breeze. In short, the expressive power of dynamics is quite rich, and it can be said that it is a musical element rich in "magic".

Dynamics are often Italian musical terms. Composers mark detailed dynamics on the score, which can usually be divided into more than a dozen levels from the weakest to the strongest, and the intensity of each level is a relative value.

Piano means weak, abbreviated as P. The more P, the weaker. There can be up to 5 P, which means extremely weak. Forte means strong, abbreviated as f. The more f's, the stronger. If there are five f's marked on the score, it is quite strong, and the performer must play with all his strength.