Getting music in: YouTube and Spotify

What each service actually permits, what SHAWZIFY does with that, and why the two are used together rather than either alone.

Spotify: exact identity, no audio

Spotify's Web API is excellent at saying what a track is and refuses to give you the track. Both halves matter.

What was removed, and when

On 27 November 2024 Spotify restricted a group of endpoints for any application registered after that date (announcement):

Apps that already had extended access keep it; everything registered since gets 403. There is no official replacement.

audio-features is the one that would have been tempting — it returned tempo, key, mode, time signature, energy and valence. It is worth being clear that losing it costs SHAWZIFY almost nothing: the product measures all of that from the audio itself, because it has to transcribe the notes anyway. A tempo number from an API is no use without the notes it belongs to.

What still works, and what SHAWZIFY uses

With client-credentials auth (the user's own app, created at developer.spotify.com/dashboard):

• GET /tracks/{id} — name, artists, album, duration, ISRC, artwork
• GET /albums/{id} and GET /playlists/{id}/tracks
• GET /search

SHAWZIFY uses exactly this and nothing else. The duration in particular is load-bearing: it is how a resolved recording is checked against the track that was asked for.

Credentials live in %LOCALAPPDATA%\Shawzify\spotify.json or in SPOTIFY_CLIENT_ID / SPOTIFY_CLIENT_SECRET. Without them the provider reports itself unavailable and says how to enable it; nothing else breaks.

SpotifyProvider.fetch() never pretends. It raises an error that says Spotify does not allow applications to download audio, and points at the alternative.

YouTube: audio, and a lot of near-misses

yt-dlp is an optional dependency, deliberately not bundled: it is a fast-moving tool that breaks and gets fixed on a weekly cadence, and users are better off running pip install -U yt-dlp themselves than waiting for a SHAWZIFY release. When it is absent the route is disabled with that instruction.

What SHAWZIFY does:

• Reads metadata without downloading, so pasting a link shows what it is first.
• Downloads the best audio-only stream, without re-encoding — the container goes straight to SHAWZIFY's own FFmpeg. Faster, and it avoids depending on yt-dlp finding an ffprobe that the bundled FFmpeg does not ship.
• Refuses anything over 20 minutes. A two-hour mix is never the intended input.
• Caches by video id, metadata included, so re-opening a track is instant and works offline.

Putting them together

A Spotify link goes: metadata from Spotify → search YouTube → verify → download.

The verification step is the interesting part, because a search for "Artist - Title" returns the studio version alongside live versions, covers, karaoke tracks, sped-up edits, "8D audio", and one-hour loops. Each candidate is scored on:

Two details make it work in practice:

• Variant markers are matched against the un-stripped title. Titles are normalised for comparison by removing bracketed decoration, but the markers live inside exactly those brackets — Photograph [1 hour]. Searching the stripped text would miss every one of them.
• A gross duration mismatch caps the total score. An hour-long upload matches title and artist perfectly; without the cap, text agreement alone carries it to a respectable score. Both cases are regression-tested.

The chosen match and its confidence are always reported. Below 60% the UI says the match is uncertain, and --candidate N (CLI) picks a different result.

Legality and scope

• Local files remain the primary input. Every link route is optional and can be absent without affecting anything else.
• Nothing here bypasses access control, DRM or authentication. yt-dlp fetches what a browser fetches from a public page.
• Downloads land in the user's own cache and are never uploaded anywhere.
• SHAWZIFY exists to transcribe music onto a twelve-note game instrument. Do not use it to reproduce or redistribute music you do not have the right to.

Usage

# Straight to a song code
shawzify convert "https://www.youtube.com/watch?v=..." --focus hook

# Spotify: identified by Spotify, heard via YouTube
shawzify convert "https://open.spotify.com/track/..."

# Just the audio
shawzify fetch "https://youtu.be/..." -o song.m4a
shawzify fetch "https://youtu.be/..." --candidate 2   # a different search result

In the app, paste a link on the home screen. It identifies the track as you pause typing, then Convert fetches and arranges it.