Chang is a string instrument which flourished in Persia in many forms from its introduction, about 3000 B.C.E., until the 17th century. The original type was the arched harp as seen at Chogha Mis and on later third millennium seals. Around 1900 B.C.E. they were replaced by angular harps with vertical or horizontal sound boxes.
By the start of the Common Era, “robust, vertical, angular harps”, which had become predominant in the Hellenistic world, were cherished in the Sasanian court. In the last century of the Sasanian period, angular harps were redesigned to make them as light as possible (light, vertical, angular harps); while they became more elegant, they lost their structural rigidity. At the height of the Persian tradition of illustrated book production (1300 to 1600 C.E.), such light harps were still frequently depicted, although their use as musical instruments was reaching its end.

Third millennium B.C.E.
This was the era of arched harps in Persia. It came to an end with the arrival of angular harps, ca. 1900 B.C.E.
Angular harps, one of the earliest depictions of which features in a terracotta plaque from Sahr-e Sokhta in eastern Persia, were mostly vertical at first. Although its exact date of origin is unclear (since it was a surface find, the dating is uncertain and the excavator’s suggestion of 3000 to 2300 B.C.E. seems too early), together with the Chogha Mis seal it indicates that Persians may have then been the most active producers of harps in this era.

Second and first millennia B.C.E.
The largest source of early depictions of angular harps is terracotta plaques made in Mesopotamia during the Isin/Larsa and Old Babylonian periods. The side view was especially popular, but other views from the side and front were also depicted.
Terracotta plaques from Susa (1970-1650 B.C.E.) contain depictions of Persian angular harps that differ consistently from those in Mesopotamia: while their shapes are similar, the Persian harps are smaller in size.
In both of these depictions the Mesopotamian harp extends from the player’s navel to a point above his head by approximately the length of his head.
Elamite-Persian harp is less than half as tall as the Mesopotamian harp. There is a similar discrepancy between the horizontal, angular harps from the two regions. The size of the Mesopotamian horizontal harp is approximately the same as the Mesopotamian vertical harp, but the Elamite-Persian instrument is less than half the size.
There are many Persian representations of harps dating from between the 12th and 7th century B.C.E. For example, large rock reliefs at Kul-e Fara, near Idha, show ensembles of vertical and horizontal harps which are as large as Mesopotamian ones. Equally large are the vertical and horizontal harps played outside the Persian city of Madaktu, captured by Assurbanipal ca. 645 B.C.E. Although harps were most often played in large homogeneous ensembles, the Arjan bowl depicts a heterogeneous group playing harps, lute, lyre, pipes, cymbals, and drums, as well as dancing, juggling and stilt walking.

Parthian and Sasanian periods
Parthian harps were typical of the Hellenistic genre, and so it is difficult to determine if they were derived from an indigenous tradition or from a western (Egyptian and Greek) one. The Hellenistic harp had a straight box which sometimes expanded towards the top, and its rod had a wide girth.
In the Sasanian period the Hellenistic tradition continued, as demonstrated on a mosaic at Bisapur. Harps on silver vessels, which are dated slightly later, were as robust in form as Hellenistic harps, but their curved tops indicate Central Asian influence. Horizontal, angular harps are shown in Taq-e Bostan, and even as late as on an 8th-10th century C.E. silver plate. The Taq-e Bostan reliefs show a royal hunt accompanied by music; only harps were allowed on the king’s boat and on the accompanying barge, suggesting that they had become closely associated with royalty in the Sasanian period. As mentioned above, this period also witnessed the introduction of the light, angular harp, which became the most common type during the Islamic period. (Source: The Circle of Ancient Iranian Studies)