Calculation:
Extension Angle of the Orchestra or the Scene (Orchestra Angle) ●
That is the total angle seen from the microphone system
to the corners of the ensemble.

 e = Width of the orchestra, the ensemble, or the scene d = Distance to the microphone system (orchestra, ensemble) θ ′max = Sound incidence angle from center 0° to the corner of the orchestra (orchestra angle) 2 × θ ′max = Full extension angle of the orchestra

 Width of the orchestra e m Distance to the microphone system d m ↓ Extension angle of the orchestra ± ° 2 × θ ′max = °

 The geometric extension (expansion) range of the sound source is the resulting total visual angle 2 × θ ′max of the orchestra section, that are the boundaries of music ensemble, but seen from the standpoint of the microphone system.

 The expansion area is only dependent on the width e of the orchestra and the distance d of the microphone system and the ensemble. Don't mix the expansion area of the orchestra 2 × θ ′max with the invisible stereo recording angle SRA (of a microphone system) 2 × θmax.= SRA. "Visualization of stereo microphone system XY cardioid/cardioid 90°": http://www.sengpielaudio.com/Visualization-XY90-E.htm Only when the apparent "expansion range of the orchestra" matches with the invisible recording angle of the stereo microphone system SRA, the location of the image width from speaker to speaker is shown correctly on the full stereo loudspeaker base.   Der 'magische' Aufnahmebereich... oder eher der unverstandene Aufnahmewinkel von Mikrofonsystemen (Stereomikrofonen) in der Tontechnik. (German)

 The visible "extension angle of the orchestra" (orchestra angle) should never be mixed up with the invisible "Stereo Recording Angle(SRA) of the microphone system".   Stereo Recording Angle SRA = 2 × Sound incidence angle θmax

 "Stereo Recording Angle SRA dependend on Axis Angle for X/Y Coincidence Microphone Systems: Cardioid/Cardioid": http://www.sengpielaudio.com/calculator-RecordingAngleAndAxisAngle.htm