Hope Bagenal, an Acoustics scientist, divided Auditoriums into two main groups: those with cavern-like acoustics and those with open air acoustics. Out of the first group concert halls are born, and from the second one, opera houses. The acoustics of the concert hall, with its long reverberation, merges the sounds coming from different sound sources. On the contrary, the theatre acoustics separate them.

In the concert halls, the "fusion" tends to merge the sounds produced by the different instruments in the orchestra, making it so that this is perceived by the listeners as one single sound source. In opera houses, with the open air acoustics, the "separation" which is a consequence of an extremely brief duration of the reverberation time, makes it so that only the language (spoken, sung) is clear and intelligible.

The traditional configuration of the Italian opera house, the traditional "singing voice" opera house, generally works well with the orchestra in the pit (under the audience). In fact, the sound quality worsens only when the orchestra rises to the stage, above the audience. For this reason, the space assigned to the performance and listening to concerts is the "concert hall", the Auditorium.

Nonetheless, a concert can also be performed and listened to in a church, a garden, a theatre, etc. Looking at the Italian conditions, the widespread presence of "all'Italiana" opera houses in almost every city makes it so that these buildings are used for all musical shows and therefore even for instrumental, symphony or chamber music concerts. But the performance of a concert in an opera house is however, an inappropriate act.
The Acoustics of the opera house, as we have already mentioned, are generally suited neither to the performance nor the listening of an instrumental music concert.

The theatre, however, can adequately host a concert if it is equipped with an electro-acoustic system of artificial reverberation (not an amplification system) or, better yet, an Acoustic Shell for Orchestras.