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hunterFormsBS

A flexible frequency-band splitter for music source separation, organized around a single separator family that can express BS-style, mel-style, and custom layouts.

Instead of treating BS-style and mel-band layouts as separate Python entry points, this package treats them as different band-layout configurations of one core design centered on BandSplitRotator.

pip install hunterFormsBS uv add hunterFormsBS

The codebase is implemented in PyTorch, fully typed (py.typed), and designed for modular reuse so options such as PoPE, custom filter banks, and optional SageAttention acceleration can live on one aligned constructor surface.

Quick fix: size mismatch when loading a checkpoint

If loading an older BS-style checkpoint or configuration raises a size-mismatch error, check mask_estimator_depth in the configuration.

Some earlier configuration files effectively used mask_estimator_depth=1 even when stored as 2 because a later subtraction was applied. This package removes that subtraction, so the direct equivalent is:

  • set mask_estimator_depth=1

Updating that value resolves the most common mismatch quickly.

Why this architecture helps in practice

  • Forward-looking architecture: A single model family makes it easier to adopt new ideas, such as PoPE, HyperACE, or custom band-split definitions, while keeping interfaces aligned with established ecosystems.
  • Universal configuration surface: BandSplitRotator exposes downstream attention, transformer, mask-estimator, optional HyperACE segmentation-branch, STFT, and loss settings on one constructor.
  • Rich tooling and ecosystem: The package provides strong typing (py.typed), modular APIs, and rich docstrings focusing on usage, literature citations, and migration paths.

Easy to migrate

Transitioning from older codebases is straightforward because most downstream identifiers stay the same and the data flow is highly similar.

If you're changing from an existing codebase, replace the older import path with BandSplitRotator, then choose the desired band layout with freqs_per_bands, sample_rate together with num_bands, or mask_filter_bank.

What is unified here

The key design idea is that the difference between the BS-style front end and the mel-band front end is treated as a band-layout problem, not as a reason to maintain two unrelated model families.

  • hunterFormsBS.bandSplitRotator.BandSplitRotator is the primary unified entry point and the only public separator class exported by this package.
  • hunterFormsBS.bands.BandSplit, hunterFormsBS.mask.MaskEstimator, hunterFormsBS.mask.MLP, hunterFormsBS.loss.lossComputation, hunterFormsBS.attend.Attention, and hunterFormsBS.transform.Transformer hold the reusable typed building blocks shared across all band-layout modes.
  • hunterFormsBS.hyperACE.SegmModel supplies the optional segmentation-style mask-estimation branch used when use_hyperACE=True.
  • Attention and transformer options such as attn_dropout, ff_dropout, flash_attn, sage_attention, and scale keep the same identifiers as they move from model constructors into downstream blocks.
  • All user-configurable separator settings live on BandSplitRotator, including optional HyperACE branch settings under the segm_* prefix.

At the band level, the model only needs a band-membership map, called mask_filter_bank in the codebase. You can think of that map as a Boolean matrix

$$ F \in {0, 1}^{B \times N_f} $$

where $B$ is the number of bands and $N_f$ is the number of STFT frequency bins.

  • In a non-overlapping BS-style layout, each frequency bin belongs to exactly one band, so

$$ \forall f,; \sum_b F_{b,f} = 1. $$

  • In an overlapping mel-style layout, some frequency bins belong to more than one band, so

$$ \exists f \text{ such that } \sum_b F_{b,f} > 1. $$

When bands overlap, the reconstructed mask for a frequency bin is averaged across the contributing bands:

$$ \hat{M}_{f,t} = \frac{1}{S_f} \sum_{b : F_{b,f} = 1} \hat{M}^{(b)}_{f,t}, \qquad S_f = \sum_b F_{b,f}. $$

That is why this package makes it easy to move between overlapping and non-overlapping bands, and to change how bands are distributed across the frequency axis. The architectural difference lives in the filter bank, not in two separate theories of the model.

Which band-layout mode you should use

Use this configuration When Key parameters
BandSplitRotator with the default non-overlapping layout You want a BS-style frequency partition or a close comparison with non-overlapping upstream layouts. freqs_per_bands, optional num_bands
BandSplitRotator with automatic mel-band construction You want a mel-band layout computed at runtime. sample_rate, num_bands, melscale_fbanks_mel_scale, melscale_fbanks_norm
BandSplitRotator with explicit custom bands You want a checkpoint-specific or research-specific layout. mask_filter_bank

Attention and optional acceleration

flash_attn=True requests PyTorch scaled-dot-product-attention backends when the active device supports that path. sage_attention=True asks downstream Attend blocks to call sageattention.sageattn; install SageAttention manually before enabling it because hunterFormsBS does not install that package.

BandSplitRotator can choose RoPE or PoPE with use_pope, so the same model family can switch positional encoders without changing entry points.

Automatic and custom mask_filter_bank construction

Most users never need this section. When mask_filter_bank is None and both sample_rate and num_bands are provided, BandSplitRotator builds mel-band layouts at runtime with torchaudio.functional.melscale_fbanks. The constructor parameters melscale_fbanks_mel_scale and melscale_fbanks_norm are forwarded to torchaudio, so you can choose the mel-scale formula and normalization rule used for automatic mel-band construction.

For the package default mel-band layout, keep sample_rate=44100, stft_n_fft=2048, num_bands=60, melscale_fbanks_mel_scale='slaney', and melscale_fbanks_norm='slaney'.

When sample_rate and num_bands are not both provided, BandSplitRotator derives the non-overlapping BS-style Boolean band-membership map from freqs_per_bands.

If a checkpoint uses a different band layout, pass mask_filter_bank explicitly as a Boolean torch.Tensor with shape (band, freq).

All optional segmentation-branch settings also live on BandSplitRotator under the segm_* prefix.

Package map

  • hunterFormsBS.__init__
    • Direct export: BandSplitRotator
    • Purpose: small top-level namespace for the primary separator model.
  • hunterFormsBS.bandSplitRotator
    • Main symbols: BandSplitRotator
    • Purpose: unified separator that can build BS-style, mel-style, or custom band layouts from one model family, with downstream attention, transformer, STFT, mask-estimator, optional segmentation-branch, and loss options on the constructor.
  • hunterFormsBS.bands
    • Main symbols: BandSplit, DEFAULT_FREQS_PER_BANDS
    • Purpose: band projection layer and the BS-style default frequency-bin partition.
  • hunterFormsBS.loss
    • Main symbols: lossComputation
    • Purpose: multi-resolution STFT training-loss helper.
  • hunterFormsBS.mask
    • Main symbols: MaskEstimator, MLP
    • Purpose: mask-estimation heads and band-local affine blocks.
  • hunterFormsBS.attend
    • Main symbols: Attend, Attention
    • Purpose: shared attention core with RoPE / PoPE, PyTorch SDPA, and optional SageAttention support.
  • hunterFormsBS.transform
    • Main symbols: FeedForward, Transformer
    • Purpose: position-wise feedforward block and stacked attention-and-feedforward transformer.
  • hunterFormsBS.hyperACE
    • Main symbols: SegmModel, HyperACE, Backbone, Decoder, ProgressiveUpsampleHead
    • Purpose: optional segmentation-style mask-estimation branch and its reusable building blocks.
  • hunterFormsBS.theTypes
    • Main symbols: ParametersComputeLoss, FlashAttentionConfig, ParametersAttention, ParametersMaskEstimator, ParametersSTFT, ParametersTransformer
    • Purpose: typed configuration records used across the package.

Architecture in one sentence

The stable separator path is

raw audio → STFT → band gathering → BandSplit → hierarchical attention → MaskEstimator → mask

followed by overlap-aware mask averaging when needed, complex masking in the STFT domain, and inverse STFT reconstruction back to waveform audio.

When use_hyperACE=True, each MaskEstimator head also adds the optional segmentation-style branch before the final mask accumulation step.

Top-level exports

The top-level package namespace currently re-exports the primary model that new users most often need:

  • BandSplitRotator

Supporting modules stay under explicit submodule imports so the main namespace remains small and comparisons with upstream repos stay easy to read.

Reference materials

Gaussian Error Linear Units (GELUs)

Language Modeling with Gated Convolutional Networks

Attention Is All You Need

Root Mean Square Layer Normalization

RoFormer: Enhanced Transformer with Rotary Position Embedding

XCiT: Cross-Covariance Image Transformers

FlashAttention: Fast and Memory-Efficient Exact Attention with IO-Awareness

SageAttention: Accurate 8-Bit Attention for Plug-and-play Inference Acceleration

SageAttention2: Efficient Attention with Thorough Outlier Smoothing and Per-thread INT4 Quantization

SageAttention2++: A More Efficient Implementation of SageAttention2

Einops: Clear and Reliable Tensor Manipulations with Einstein-like Notation

Music Source Separation with Band-Split RoPE Transformer

Mel-RoFormer for Vocal Separation and Vocal Melody Transcription

Sound Demixing Challenge 2023 Music Demixing Track Technical Report: TFC-TDF-UNet v3

Music Source Separation Based on a Lightweight Deep Learning Framework (DTTNET: DUAL-PATH TFC-TDF UNET)

YOLOv13: Real-Time Object Detection with Hypergraph-Enhanced Adaptive Visual Perception

Decoupling the "What" and "Where" With Polar Coordinate Positional Embeddings

Packages and documentation

My recovery

Static Badge YouTube Channel Subscribers

CC-BY-NC-4.0

About

Universal frequency-band splitter for music source separation: one interface for BSRoformer, MelBandRoformer, or any Band Split. RoPE, PoPE, HyperACE. Documentation, citations, and explanations. PyTorch; CUDA-accelerated.

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machine-learning artificial-intelligence source-separation music-source-separation audio-source-separation melbandroformer bs-roformer

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Releases 11

0.3.1 Latest
Jun 10, 2026
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