Subtractive Training for Music Stem Insertion using Latent Diffusion Models
Ivan Villa-Renteria, Mason L. Wang, Zachary Shah, Zhe Li, Soohyun Kim, Neelesh Ramachandran, Mert Pilanci
TL;DR
The paper tackles the problem of generating missing musical stems that coherently integrate with existing context by reframing stem insertion as spectrogram editing guided by text instructions. It introduces Subtractive Training, which uses triplets of (full-mix, stem-subtracted, edit instruction) and fine-tunes a pre-trained text-to-audio latent diffusion model to learn $p(oldsymbol{x}ig|oldsymbol{y},oldsymbol{x}_{partial})$, enabling context-aware insertion of stems. Empirically, the method yields realistic drum accompaniments and enables stem-wise style control, with the MIDI extension producing compatible bass, drum, and guitar parts. This approach offers a scalable, text-guided framework for editing full musical arrangements at the stem level, supporting creative rearrangements while preserving other instruments.
Abstract
We present Subtractive Training, a simple and novel method for synthesizing individual musical instrument stems given other instruments as context. This method pairs a dataset of complete music mixes with 1) a variant of the dataset lacking a specific stem, and 2) LLM-generated instructions describing how the missing stem should be reintroduced. We then fine-tune a pretrained text-to-audio diffusion model to generate the missing instrument stem, guided by both the existing stems and the text instruction. Our results demonstrate Subtractive Training's efficacy in creating authentic drum stems that seamlessly blend with the existing tracks. We also show that we can use the text instruction to control the generation of the inserted stem in terms of rhythm, dynamics, and genre, allowing us to modify the style of a single instrument in a full song while keeping the remaining instruments the same. Lastly, we extend this technique to MIDI formats, successfully generating compatible bass, drum, and guitar parts for incomplete arrangements.
