“to play.” The Hebrew word is general and can refer to different types of play, including singing and dancing, but the context almost certainly involves sexual play as well, which was standard in the worship of a fertility god. Sexual revelry broke out later in the wilderness wanderings as well (Nu. 25:1-15). It seems if all the people did was dance before the idol, the text would have used a more specific word, and besides, the Israelites could sing and dance before Yahweh if all they wanted to do was to sing and dance. But in contrast to an Egyptian bull-god that would have encouraged all kinds of sexual activity, God, in the Book of the Covenant that the Israelites had just agreed to, was very pure when it came to sex. Marry, do not commit adultery, do not covet your neighbor’s wife, etc.
The golden calf idol no doubt came from the many years Israel had spent in Egypt, and the worship of the bull god Apis was very popular in Egypt, although the bull-gods of Mnevis and Buchis were also worshiped. The bull was a symbol of fertility and strength, and was also linked with the afterlife. The fact that the Israelites made a calf god is more good evidence that sex was a prime motivator in the making of this particular god and that the worship of it would have involved sexual activity.