Beyond Piano: Cross-Instrument MIDI Velocity Estimation via Differentiable SoundFont Proxies

Zhanhong He; Hanyu Meng; David Defeng Huang; Roberto Togneri

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arXiv · 2608.08985

Beyond Piano: Cross-Instrument MIDI Velocity Estimation via Differentiable SoundFont Proxies

Zhanhong He·Hanyu Meng·David Defeng Huang·Roberto Togneri

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Abstract

Many music datasets contain MIDI notes but lack reliable velocities, defaulting to a constant value. This absence is especially problematic outside the piano domain, as velocity is a core component for expressive rendering, music generation, and performance analysis. This paper studies cross-instrument MIDI velocity estimation in this label-scarce setting. Starting from a piano-trained velocity estimator, we recast target-instrument adaptation as predicting renderer-conditioned velocities whose rendering matches the dynamics of the performance audio. This adaptation can be driven by either differentiable synthesizers (Diff-Synth) or our proposed differentiable SoundFont proxies (Diff-SFProxy). We highlight the Diff-SFProxy: it supervises velocity through note-wise, loudness-related acoustic parameters rather than waveform reconstruction, focusing gradients on velocity-dependent behavior. Experiments on piano and guitar show that Diff-SFProxy is effective for cross-instrument MIDI velocity estimation, while waveform-domain Diff-Synth degrades performance.

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BibTeX RIS

Zhanhong He, Hanyu Meng, David Defeng Huang, Roberto Togneri. 2026-08-10. Beyond Piano: Cross-Instrument MIDI Velocity Estimation via Differentiable SoundFont Proxies. https://arxiv.org/abs/2608.08985

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