This parallel recording compares the very dry, precise studio sound (here in the acoustics of the Teldex studio, a studio orchestra and the sound of a New York Steinway from the 1950s), with a sound that one might expect in a modern concert hall (here the acoustics of the Berlin Philharmony, a large symphonic Orchestra and a current German Steinway D).
Beside the original "Vocalise" op.34/14 for textless Voice and piano (which is often enough also played as it is just with another Soloinstrument instead of the Soprano and piano), Rachmaninov himself wrote also two different orchestral arrangements of this "Vocalise", one for voice and Orchestra, and another with notable changes in the Winds for Soloviolin and Orchestra.