A method performed by an audio encoder for handling input envelope representation coefficients, the method comprising: applying a two-stage vector quantization, wherein the two-stage VQ comprises a first stage split VQ and a second stage pyramid vector quantization, by: quantizing the input envelope representation coefficients by applying the first stage split VQ to obtain quantized envelope representation coefficients; determining envelope representation residual coefficients by subtracting the quantized envelope representation coefficients from the input envelope representation coefficients; transforming the envelope representation residual coefficients into a warped domain to obtain transformed envelope representation residual coefficients; quantizing the transformed envelope representation residual coefficients by applying the second stage PVQ, where at least one of a plurality of gain-shape coding schemes is applied on the transformed envelope representation residual coefficients in order to achieve gain-shape coded envelope representation residual coefficients, where the plurality of gain-shape coding schemes have mutually different trade-offs in one or more of gain resolution and shape resolution for one or more of the transformed envelope representation residual coefficients; and providing the gain-shape coded envelope representation residual coefficients and information on the at least one applied gain-shape coding scheme to a multiplexor (623, 1406) to be multiplexed into a joint index for subsequent transmission to an audio decoder. applying a two-stage vector quantization, wherein the two-stage VQ comprises a first stage split VQ and a second stage pyramid vector quantization, by: quantizing the input envelope representation coefficients by applying the first stage split VQ to obtain quantized envelope representation coefficients; determining envelope representation residual coefficients by subtracting the quantized envelope representation coefficients from the input envelope representation coefficients; transforming the envelope representation residual coefficients into a warped domain to obtain transformed envelope representation residual coefficients; quantizing the transformed envelope representation residual coefficients by applying the second stage PVQ, where at least one of a plurality of gain-shape coding schemes is applied on the transformed envelope representation residual coefficients in order to achieve gain-shape coded envelope representation residual coefficients, where the plurality of gain-shape coding schemes have mutually different trade-offs in one or more of gain resolution and shape resolution for one or more of the transformed envelope representation residual coefficients; and quantizing the input envelope representation coefficients by applying the first stage split VQ to obtain quantized envelope representation coefficients; determining envelope representation residual coefficients by subtracting the quantized envelope representation coefficients from the input envelope representation coefficients; transforming the envelope representation residual coefficients into a warped domain to obtain transformed envelope representation residual coefficients; quantizing the transformed envelope representation residual coefficients by applying the second stage PVQ, where at least one of a plurality of gain-shape coding schemes is applied on the transformed envelope representation residual coefficients in order to achieve gain-shape coded envelope representation residual coefficients, where the plurality of gain-shape coding schemes have mutually different trade-offs in one or more of gain resolution and shape resolution for one or more of the transformed envelope representation residual coefficients; and providing the gain-shape coded envelope representation residual coefficients and information on the at least one applied gain-shape coding scheme to a multiplexor (623, 1406) to be multiplexed into a joint index for subsequent transmission to an audio decoder.