This paper discusses Head Related Transfer Function (HRTF) based artificial spatialisation of audio. Two alternatives to the minimum phase method of HRTF interpolation are suggested, offering novel approaches to the challenge of phase interpolation. A phase truncation, magnitude interpolation technique aims to avoid complex preparation, manipulation or transformation of empirical HRTF data, and any inaccuracies that may be introduced by these operations. A second technique adds low frequency non-linear frequency scaling to a functionally based phase model. This approach aims to provide a low frequency spectrum more closely aligned to the empirical HRTF data. Test results indicate favorable performance of the new techniques.