with k fq t q , t k being an asymmetric kernel with coefficients inferred by f q : log k fq t q , t k = ∑ (iii) Relative Positional Embedding of Shaw et al. (2018) and Music <cite>Transformer</cite> (Huang et al., 2018b) : t ⋅ represents the indicator of the position in the sequence, and the kernel is modified to be indexed by a look-up table: