NAudio 3 is a major release. The single NAudio assembly is now split into focused, independently usable packages; the minimum target framework moves to net9.0; the core is cross-platform and Native-AOT compatible; and several large new subsystems — a cross-platform effects suite, a software sampler, VST 3 hosting, and ALSA and libsndfile backends — join the library. The headline changes are below; see the linked tutorials and the per-package READMEs for the detail.

Packages and platform

• Minimum target framework is now net9.0 — legacy .NET Framework and .NET Standard 2.0 support is dropped
• NAudio is now a set of focused packages: NAudio.Core, NAudio.Midi, NAudio.WinMM, NAudio.Wasapi, NAudio.Asio, NAudio.WinForms, NAudio.Dmo, plus the new NAudio.Effects (in NAudio.Core), NAudio.Sampler, NAudio.Vst3, NAudio.Alsa and NAudio.SoundFile. The NAudio meta-package still pulls the Windows stack together so existing consumers see no change. See Docs/Architecture/NAudio3AssemblyLayoutPlan.md
• NAudio.Core, NAudio.Midi and NAudio.Wasapi are Native-AOT compatible (IsAotCompatible=true), enforced in CI by NAudioAotSmokeTest. NAudio.Midi, NAudio.Effects, NAudio.Sampler and NAudio.SoundFile are cross-platform

New capabilities

Each new subsystem has its own tutorial/README; only the headline is listed here.

• Audio effects — a cross-platform NAudio.Effects framework: IAudioEffect / EffectSampleProvider / EffectChain with click-free bypass, dry/wet mix and an optional parameter model, plus a broad effect set (EQ and filtering, dynamics, saturation/lo-fi, delay and modulation, reverb including FFT convolution, pitch shifting, and voice-comms AGC/noise-suppression). See Docs/AudioEffects.md
• Software sampler — new NAudio.Sampler package: polyphonic, cross-platform playback of SoundFont (.sf2) and SFZ instruments and single-sample instruments, rendered as an ISampleProvider (SF2 modulator engine, DAHDSR envelopes, LFOs, modulated filters, reverb/chorus sends, voice stealing, choke groups). See Docs/Sampler.md
• VST 3 hosting (preview) — new NAudio.Vst3 package (Windows-only): discover, load and host VST 3 effects and instruments, with parameters, state and .vstpreset presets, native editor windows, program lists/units, latency compensation, and live/offline MIDI-file playback through the shared MIDI pipeline. See the NAudio.Vst3 README and Docs/Architecture/Vst3Hosting.md. VST is a registered trademark of Steinberg Media Technologies GmbH
• Cross-platform audio files — new NAudio.SoundFile package: read and write WAV/AIFF/FLAC/Ogg-Vorbis/Opus/MP3 via a system libsndfile on Windows, Linux and macOS (the first cross-platform FLAC/Vorbis/Opus encoder in NAudio). See Docs/CrossPlatformAudioFilesWithSoundFile.md (#1289)
• Linux audio — new NAudio.Alsa package: AlsaOut (IWavePlayer) and AlsaIn (IWaveIn) plus AlsaDeviceEnumerator, backed by libasound. See Docs/PlayAudioFileLinuxAlsa.md and Docs/RecordAudioFileLinuxAlsa.md (#1182)
• Sequencing — a portable NAudio.Sequencing namespace in NAudio.Core (tempo and time-signature maps, transport, EventTimeline, swing, and a sample-accurate per-buffer dispatcher) underpinning MIDI-file playback and the sampler. See Docs/Architecture/Sequencing.md
• Modern WASAPI and ASIO — high-level WasapiPlayer / WasapiRecorder (built via WasapiPlayerBuilder / WasapiRecorderBuilder: IAudioClient3 low-latency, MMCSS, IAsyncDisposable, zero-copy buffers, process-loopback capture), and a new AsioDevice replacing AsioOut (explicit playback/recording/duplex modes, non-contiguous channels, per-channel Span<float> callbacks, driver-reset recovery, per-buffer timing). See Docs/WasapiPlayer.md, Docs/WasapiRecorder.md and Docs/AsioMigration.md
• MIDI — NAudio.Midi is now cross-platform; new WinRT WinRTMidiIn / WinRTMidiOut (in NAudio.Wasapi) and backend-agnostic IMidiInput / IMidiOutput; a new IMidiInstrument seam with MidiFileSequence / SequencedMidiPlayer / OfflineMidiRenderer / LiveMidiInstrument gives an end-to-end MIDI-file → audio pipeline that drives the sampler or a hosted VST 3 instrument. MidiFile now also reads RIFF-RMID (.rmi) files (#1236)
• Sample providers / DSP — new ChannelMixerSampleProvider with ready-made ChannelMixMatrix routings (mono↔stereo, stereo→5.1, …), thanks to @antiduh (#982); a new FftProcessor, an IWaveChunkInterpreter<T> extension point (cue lists, BWF bext, LIST/INFO), Span<T> overloads across the codec/DSP surface, and reusable building blocks (EnvelopeFollower, DelayLine, Lfo, Oversampler, LinkwitzRileyCrossover, PartitionedConvolver, …) underpinning the effects and sampler

Breaking changes

The full upgrade walkthrough — every breaking change with before/after code — is in Migrating from NAudio 2 to NAudio 3. Most apps need only re-target to net9.0 and adjust custom providers to the new Span<T> Read signature. The highest-impact changes:

• Minimum target framework is now net9.0 (legacy .NET Framework / .NET Standard 2.0 dropped)
• IWaveProvider.Read / ISampleProvider.Read now take a single Span<byte> / Span<float> (was buffer/offset/count) — callers migrate via source.Read(buffer.AsSpan(offset, count)); implementations override the span method
• WasapiOut, WasapiCapture and WasapiLoopbackCapture are [Obsolete] in favour of WasapiPlayer / WasapiRecorder (the legacy types still ship and work); WasapiOut's embedded exclusive-mode resampler was removed
• WaveOut / WaveIn now default to event-driven callbacks; the window-based variants are renamed WaveOutWindow / WaveInWindow in NAudio.WinForms
• Some types moved package/namespace as part of the split — classic Windows MIDI I/O and winmm types to NAudio.WinMM; the DMO/DirectSound types into the new NAudio.Dmo package; plus smaller moves (AudioVolumeLevel, CaptureState, DmoMp3FrameDecompressor). Meta-package consumers are unaffected
• SimpleCompressorStream, ImpulseResponseConvolution and NAudio.Extras.Equalizer were removed — superseded by NAudio.Effects (CompressorEffect, ConvolutionReverbEffect, Equalizer)

Notable bug fixes

In addition to the fixes below, the new sampler/SFZ/SoundFont subsystem saw extensive correctness work during development — see Docs/Sampler.md.

• WaveOut: fixed a race where stopping/disposing faster than the buffer latency could throw a NullReferenceException via PlaybackStopped (#804)
• WaveFileWriter: removed the finalizer that fired an unconditional Debug.Assert and could crash the process on the finalizer thread when construction had thrown
• AudioClient.Dispose is now idempotent and safe against concurrent/re-entrant disposal, fixing an intermittent interop NullReferenceException (#1183)
• AcmInterop: serialised all msacm32 P/Invokes process-wide, fixing process-killing access violations under concurrent ACM use
• WaveFileReader / AiffFileReader: malformed headers declaring BlockAlign=0 now throw InvalidDataException from the constructor instead of DivideByZeroException later (#1254); WaveFileReader no longer throws on an oversized fmt cbSize (#482)
• WaveFormat.Serialize: PCM formats now write the canonical 16-byte fmt chunk (#934, #1098)
• WaveViewer: fixed rendering upside-down (#801, #818) and now renders any source format correctly via ToSampleProvider() (#564)
• AudioSessionControl: now supports multiple registered event clients without leaking, and UnRegisterEventClient honours its argument (#1263)
• AudioEndpointVolume.OnVolumeNotification: fixed per-channel notifications all returning channel 0's volume (#351)
• CueListInterpreter: WAV files with cue points but no labels now return cues with empty labels instead of null (#549)
• ResamplerDmoStream: fixed an infinite loop on Read after seeking and the loss of the resampler tail at end-of-stream (#607, #608)
• LoopStream.Read: no longer spins at 100% CPU when the wrapped source can't satisfy a read (#1338)
• Mp3FileReader: fixed false sample-rate-change errors near end of file, and more robust MP3 frame parsing against album art / trailing metadata
• MidiFile: preserve running-status across meta events (fixes "Read too far")
• BlockAlignReductionStream.Position: validates the incoming value, so a block-aligned seek after an arbitrary read no longer wrongly throws (#368)
• MmException messages now append a human-readable MmResult description (#1192); Id3v2Tag.ReadTag no longer throws/catches for tagless MP3 streams (#265)
• ASIO: implemented missing Asio64Bit Int24LSB/Float32LSB conversions and fixed a byte-order bug in GetSamplePosition; WdlResampler backported three upstream Cockos WDL fixes
• Hardened Media Foundation and DMO interop against COM ref leaks on error paths (MediaFoundationReader, MediaFoundationEncoder, MediaFoundationTransform, MediaBuffer, Mf* wrappers) (#1293)
• Removed dead naudio.codeplex.com links from the README, MixDiff and source comments (#985)

Performance

• Vectorised mix-add and volume kernels via System.Numerics.Tensors (significantly faster on AVX2)
• WaveStream.Read(Span<byte>) is overridden directly on every concrete reader (no intermediate byte-array copy); WasapiCapture's path is now zero-copy via the native WASAPI buffer span
• Eliminated per-Read allocations in SmbPitchShiftingSampleProvider, ResamplerDmoStream and DmoMp3FrameDecompressor (#971)
• Mp3FileReader builds its table-of-contents lazily on first seek; the Position setter no longer blocks and rapid scrub seeks debounce
• The sampler and sequencer render allocation-free and lock-free on the audio thread (control-rate envelope/LFO advancement, indexed region lookup, copy-on-write event timelines)

Tooling, packaging and modernisation

• Most COM interop migrated from [ComImport] to [GeneratedComInterface] / ComWrappers, and many P/Invokes to [LibraryImport], across the WASAPI/Core Audio activation chain, Media Foundation, the DMO interfaces, DirectSound and the ComStream CCW
• Codebase-wide code-style sweep (file-scoped namespaces, target-typed new, string interpolation, …) now enforced at build time via .editorconfig / .globalconfig; added .git-blame-ignore-revs so the mechanical commits don't obscure git blame
• Each NAudio package now ships its own README and embeds an SPDX 2.2 SBOM under /_manifest/spdx_2.2/ in its .nupkg, and carries per-package <Description> metadata
• Tests migrated from VSTest to Microsoft.Testing.Platform, and NAudioTests split into cross-platform NAudio.Core.Tests and Windows-only NAudio.Windows.Tests; migrated to the .slnx solution format; renamed license.txt to LICENSE
• Added a DocFX documentation site (tutorials + API reference) published to GitHub Pages, built from Docs/ and the source XML comments

Demos and test harnesses

• New WPF demo modules for the new subsystems: Convolution Reverb, managed Realtime Effects, VST3 Realtime Effects, VST3 Realtime Instrument, VST3 MIDI File Player, a Live MIDI Sampler and a Single-Sample Editor
• New NAudioConsoleTest CLI harness (run-batch for JSON test plans, diagnose for a structured host-audio snapshot) and MfStressTest for the new Media Foundation interop
• WPF demos: spectrum analyser rewritten (correct dB/log-frequency/calibration), new LiveWaveformControl, loopback + multi-API device selection in the WAV recording demo, and a drum machine rebuilt on the new NAudio.Sequencing primitives
• Replaced the deprecated vendored NSpeex with Opus (Concentus) in the network chat demo