This paper concerns the exploitation of multi-resolution time-frequency features via Wavelet Packet Transform to improve audio onset detection. In our approach, Wavelet Packet Energy Coefficients (WPEC) and Auditory Spectral Features (ASF) are processed by Bidirectional Long Short-Term Memory (BLSTM) recurrent neural network that yields the onsets location. The combination of the two feature sets, together with the BLSTM based detector, form an advanced energy-based approach that takes advantage from the multi-resolution analysis given by the wavelet decomposition of the audio input signal. The neural network is trained with a large database of onset data covering various genres and onset types. Due to its data-driven nature, our approach does not require the onset detection method and its parameters to be tuned to a particular type of music. We show a comparison with other types and sizes of recurrent neural networks and we compare results with state-of-the-art methods on the whole onset dataset. We conclude that our approach significantly increase performance in terms of F-measure without any music genres or onset type constraints.