Odeon

The other building type similar to theatres, although smaller and generally roofed, was the odeon. Unlike theatres and amphitheatres, odea were not built in all of the larger Roman towns, although they became more common in the second century ad.

Source: wiktionary

However, the significance of this transformation should not be overstated: it was not converted in to a church until the 6th c., and political meetings are attested in the nearby odeon, from late acclamations. Sagalassos is in fact the only eastern bouleuterion to show decay in the 5th c. Other examples are known that are generically dated to Late Antiquity: from Aizanoi and Ptolemais, both with bouleuteria-odea converted to aquatic spectacles, from Selge, where the building was converted into a church, and from Seleuceia-Lyrbe, where the building seems to have been transformed into a row of shops.

Source: wiktionary

Based on its small size, the excavators have suggested it may have been an odeon with a seating capacity of between 150 and 200 people; see Uziel, Lieberman, and Solomon (2019, 245–48). Odea were, initially at least, designed for small-scale concerts and recitals; but this distinction blurred over time and varied depending upon the size and resources of individual cities.

Source: wiktionary