A method of encoding an input audio stream having one or more audio components, wherein each audio component is associated with a spatial location, the method including the steps of: rendering a first playback stream presentation of said input audio stream, said first playback stream presentation is a set of M1 signals intended for reproduction on a first audio reproduction system; rendering a second playback stream presentation of said input audio stream, said second playback stream presentation is a set of two signals intended for reproduction on a second audio reproduction system, wherein one of the first playback stream presentation and the second playback stream presentation is a loudspeaker presentation and wherein the other one of the first playback stream presentation and the second playback stream presentation is an echoic or anechoic binaural presentation; characterized by: determining a set of transform parameters suitable for transforming an intermediate playback stream presentation, which is a set of M3 signals, to an approximation of the second playback stream presentation, wherein the set of transform parameters are matrix coefficients of a M3x2 matrix which, when applied to the intermediate playback stream presentation by matrix multiplication, generate the approximation of the second playback stream presentation, and wherein the intermediate playback stream presentation is one of the first playback stream presentation and a down-mix of the first playback stream presentation; wherein the transform parameters are determined by minimization of a measure of a difference between the second playback stream presentation and the approximation of the second playback stream presentation generated by application of the transform parameters to the intermediate playback stream presentation; and encoding the first playback stream presentation and said set of transform parameters for transmission to a decoder. rendering a first playback stream presentation of said input audio stream, said first playback stream presentation is a set of M1 signals intended for reproduction on a first audio reproduction system; rendering a second playback stream presentation of said input audio stream, said second playback stream presentation is a set of two signals intended for reproduction on a second audio reproduction system, wherein one of the first playback stream presentation and the second playback stream presentation is a loudspeaker presentation and wherein the other one of the first playback stream presentation and the second playback stream presentation is an echoic or anechoic binaural presentation; characterized by: determining a set of transform parameters suitable for transforming an intermediate playback stream presentation, which is a set of M3 signals, to an approximation of the second playback stream presentation, wherein the set of transform parameters are matrix coefficients of a M3x2 matrix which, when applied to the intermediate playback stream presentation by matrix multiplication, generate the approximation of the second playback stream presentation, and wherein the intermediate playback stream presentation is one of the first playback stream presentation and a down-mix of the first playback stream presentation; wherein the transform parameters are determined by minimization of a measure of a difference between the second playback stream presentation and the approximation of the second playback stream presentation generated by application of the transform parameters to the intermediate playback stream presentation; and encoding the first playback stream presentation and said set of transform parameters for transmission to a decoder. determining a set of transform parameters suitable for transforming an intermediate playback stream presentation, which is a set of M3 signals, to an approximation of the second playback stream presentation, wherein the set of transform parameters are matrix coefficients of a M3x2 matrix which, when applied to the intermediate playback stream presentation by matrix multiplication, generate the approximation of the second playback stream presentation, and wherein the intermediate playback stream presentation is one of the first playback stream presentation and a down-mix of the first playback stream presentation; wherein the transform parameters are determined by minimization of a measure of a difference between the second playback stream presentation and the approximation of the second playback stream presentation generated by application of the transform parameters to the intermediate playback stream presentation; and encoding the first playback stream presentation and said set of transform parameters for transmission to a decoder.