Cc. Antya 1.134

rāya kahe,—“kon āmukhe pātra-sannidhāna?”
rūpa kahe,—“kāla-sāmye 'pravartaka' nāma”

rāya kahe—Rāmānanda Rāya says; kon—what; āmukhe—by introduction; pātra-sannidhāna—presence of the players; rūpa kahe—Śrīla Rūpa Gosvāmī replies; kāla-sāmye—in agreement of time; pravartaka nāma—the introduction called pravartaka.

Rāmānanda Rāya inquired, “How have you introduced the assembly of the players?” Rūpa Gosvāmī replied, “The players assemble at a suitable time under the heading of pravartaka.

In a drama all the actors are called pātra, or players. This is stated by Viśvanātha Kavirāja in the Sāhitya-darpaṇa (6.283):

divya-martye sa tad-rūpo
miśram anyataras tayoḥ
sūcayed vastu-bījaṁ vā-
mukhaṁ pātram athāpi vā

The meaning of āmukha is stated by Śrīla Rūpa Gosvāmī in the Nāṭaka-candrikā:

sūtra-dhāro naṭī brūte
sva-kāryaṁ pratiyuktitaḥ
prastutākṣepicitroktyā
yat tad āmukham īritam

When Śrīla Rāmānanda Rāya inquired about the arrangement for introducing the assembly of players in the drama, Rūpa Gosvāmī replied that when the players first enter the stage in response to the time, the introduction is technically called pravartaka. For an example one may consult the Antya-līlā, First Chapter, verse 17. Śrīla Bhaktisiddhānta Sarasvatī Ṭhākura says that the introduction, which is technically called āmukha, may be of five different kinds, according to the Sāhitya-darpaṇa (6.288):

udghātyakaḥ kathodghātaḥ
prayogātiśayas tathā
pravartakāvalagite
pañca prastāvanā-bhidāḥ

Introductions may be classified as follows: (1) udghātyaka, (2) kathodghāta, (3) prayogātiśaya, (4) pravartaka and (5) avalagita. These five kinds of introduction are called āmukha. Thus Śrīla Rāmānanda Rāya asked which of the five introductions had been employed, and Śrīla Rūpa Gosvāmī replied that he had used the introduction called the pravartaka.