Technical sheet
NAUPLY Stems: the technical sheet
Facts checked on
The facts about NAUPLY Stems, NAUPLY's stem splitter: a desktop plugin (VST3, AU, standalone app) and an Android app. Every figure comes from our own measurements, with the machine used. Nothing is rounded in the product's favour.
Key facts
- NAUPLY Stems splits a song into stems entirely on the device: no audio is uploaded to the internet.
- On desktop: 2 stems in the Free edition, up to 6 in Premium, up to 10 in Pro (vocals, drums, bass, guitar, piano, other, then kick, snare, toms and cymbals).
- Models: Demucs (htdemucs, htdemucs_ft, htdemucs_6s, MIT licence) and drumsep (MIT) for drum parts; MIDI transcription by basic-pitch (Apache 2.0).
- Measured on an M1 Pro Mac: about 9 s of processing per minute of music for 4 stems at BASIC, 32 s at MEDIUM, 73 s at MAXIMUM.
- Android app: 2 stems (vocals and instrumental) computed on the phone, Quality mode (htdemucs) or Fast mode (Spleeter).
- One Stems licence covers one computer and one Android phone; Premium and Pro are available as a lifetime purchase.
Editions, stems and models (desktop)
The plugin comes in three editions. The limits are enforced by the processing itself, not only by the interface.
| Free | Premium | Pro | |
|---|---|---|---|
| Number of stems | 2 (vocals, instrumental) | 2, 4 or 6 | 2, 4, 6, 8 or 10 |
| Separated stems | Vocals, instrumental | Vocals, drums, bass, guitar, piano, other | The 6 + kick, snare, toms, cymbals |
| Separation quality | BASIC | BASIC, MEDIUM | BASIC, MEDIUM, MAXIMUM |
| Models used | htdemucs | htdemucs, htdemucs_ft, htdemucs_6s | htdemucs, htdemucs_ft, htdemucs_6s, drumsep |
| MIDI transcription of stems | No | No | Yes (basic-pitch) |
| Tempo lock to the project | No | No | Yes |
| Per-stem EQ, pitch, speed, transpose | No | Yes | Yes |
| Per-stem effects (gate, compressor, saturation, limiter, delay, reverb) | No | No | Yes |
- 8 and 10 stems: no local model splits 10 stems in one go. Stems first separates 6 stems (htdemucs_6s), then splits the drums stem with drumsep. The drum parts therefore come from the drums stem, not from the original recording, and this second pass makes processing longer.
- Demucs (Meta): MIT licence. drumsep: MIT licence. basic-pitch (Spotify): Apache 2.0 licence.
BASIC, MEDIUM and MAXIMUM quality
Quality is chosen in the plugin, with a fine setting from 0 to 100. The higher the quality, the longer the processing.
| Quality | Main model | Shifted passes | Overlap | Extra |
|---|---|---|---|---|
| BASIC (0 to 34) | htdemucs (htdemucs_6s above 4 stems) | 0 | 25% | — |
| MEDIUM (35 to 74) | htdemucs_ft | 1 | 25% | Vocals averaged with htdemucs_6s |
| MAXIMUM (75 to 100) | htdemucs_ft | 2 (3 from 95) | 35% | Averaged vocals and a filter against bleed into the vocals |
- The stems sum back to the original song (difference below 10⁻⁶) and results are reproducible: two separations of the same song give the same file.
Measured separation times
Desktop: seconds of processing per minute of music, model loading included, measured on an Apple Silicon M1 Pro Mac (GPU processing through Metal), on 35-second sequences from the MUSDB18 test set.
| Quality | 4 stems | 6 stems |
|---|---|---|
| BASIC | 8.9 s | 10.1 s |
| MEDIUM | 31.9 s | 32.7 s |
| MAXIMUM | 72.7 s | 76.0 s |
| Mode | Machine | Measurement |
|---|---|---|
| Quality (htdemucs) | M1 Pro Mac, CPU, 4 threads, same code as the app | 0.19 × the song's length (about 11 s per minute) |
| Quality (htdemucs) | Android arm64 emulator (4 virtual cores of the M1 Pro) | 60 s of music in 14.6 s |
| Fast (Spleeter) | Android arm64 emulator (4 virtual cores of the M1 Pro) | 60 s of music in 2.1 s |
- On an Intel Mac, processing runs on the CPU: it is noticeably longer (no measurement published here).
- Phones: the time depends on the processor; no measurement on a specific phone has been published yet. The app shows the remaining time during separation and can measure the phone's speed in its settings.
- 8 and 10 stems: a second pass on the drums is added (not timed here).
What stays on the device, what goes online
| Desktop | Android app | |
|---|---|---|
| Stem separation | On the computer | On the phone |
| Your audio and files | Never uploaded | Never uploaded (file names included) |
| Separation models | Installed by the installer (about 613 MiB), no download afterwards | Bundled in the app |
| Works without a connection | Yes, from 2 to 10 stems | Separation yes; the account and the monthly counter need the internet |
| What goes online | Licence activation, check every 3 months | Sign-in to the NAUPLY account, monthly separation counter |
Formats
| Desktop | Android app | |
|---|---|---|
| Accepted files | WAV, AIFF, FLAC, MP3, OGG, M4A / AAC | MP3, M4A, WAV, FLAC… and the audio of a video (MP4, MOV, WebM…) |
| Stem export | 32-bit float WAV (all editions); 24 / 16-bit WAV, AIFF and mixdown (Premium, Pro) | 16 or 24-bit WAV, 320 kbps MP3 |
| Other outputs | Drag a stem into your music software; one MIDI file per stem (Pro) | — |
| Song length | — | Up to 15 minutes |
System requirements
| Desktop | Android app | |
|---|---|---|
| System | macOS 11 or later; Windows 10 or 11 (64-bit) | Android 8.0 or later |
| Processor | Apple Silicon or Intel Mac (universal binary); x64 PC | 64-bit ARM |
| Memory | — | 4 GB (6 GB recommended) |
| Plugin formats | VST3, AU and standalone app, in any compatible music software | — |
| Storage | Models: about 613 MiB | About 37 MB per stem per minute of separated music |
| Interface languages | French, English, Spanish | French, English |
Licence and pricing
Free edition: a NAUPLY account is enough, no payment method; it is valid for 6 months from the first activation, once per account and per device.
Premium and Pro: lifetime purchase (paid once) or monthly or annual subscription, as soon as sales open. Current prices are on the product page.
One Stems licence activates on a computer and on an Android phone: the phone has its own slot and doesn't take the computer's. On the phone, the app currently separates 2 stems whatever the edition; the app's free version gives 10 separations a month, Premium and Pro have no monthly limit.
Privacy
No audio, no file and no file name leaves the computer or the phone. The Android app has no ad network, no analytics tool and no tracker.
For the licence, NAUPLY stores a device fingerprint (hashed identifier), its name and model, and the activation and check dates. The account and its data can be deleted at any time from "My account".
Listen to a real separation
14 seconds of an original NAUPLY track. Switch stems while it plays: the position is kept.
Split by NAUPLY Stems for desktop into 4 stems, MEDIUM quality (Premium and Pro editions), untouched. Each stem is brought to the same loudness so you can compare by ear; MP3 128 kbps. Song and stems: NAUPLY's own material, no third-party song.
Frequently asked questions
- Does NAUPLY Stems upload my songs to a server?
- No. Separation is computed on your computer or phone; no audio is uploaded. The internet is only used for the licence (desktop) and the account (app).
- Which AI models does NAUPLY Stems use?
- Demucs (htdemucs, htdemucs_ft, htdemucs_6s, MIT licence) for the stems, drumsep (MIT) for drum parts at 8 and 10 stems, basic-pitch (Apache 2.0) for MIDI transcription. The Android app uses htdemucs (Quality mode) and Spleeter (Fast mode, MIT).
- How long does a separation take?
- On an M1 Pro Mac, about 9 s of processing per minute of music for 4 stems at BASIC, 32 s at MEDIUM and 73 s at MAXIMUM. An Intel Mac is noticeably slower, as processing runs on the CPU.
- How many stems can I get?
- 2 in the Free edition, up to 6 in Premium and up to 10 in Pro on desktop. The Android app separates 2 stems: vocals and instrumental.
- Does Stems work without the internet?
- Yes on desktop: the models are installed with the plugin, from 2 to 10 stems. On Android, separation runs offline, but the account and the monthly counter need a connection.