mastering

name	mastering
description	Masters the mix bus in a live REAPER session — gentle corrective EQ, glue compression, and a true-peak limiter targeting a platform LUFS standard — while verifying against metering and preserving the mix's character. Use when the user asks to master, finalize, or prepare a track for Spotify/Apple/streaming or a specific loudness target. Triggers on "master this", "prepare for Spotify", "final master", "hit -14 LUFS", "/mastering".
argument-hint	[platform or LUFS target]
license	MIT
metadata	{"author":"mthines","version":"1.0.0","workflow_type":"applied","tags":["mastering","loudness","lufs","limiter","reaper","audio"]}

Mastering

Act as a mastering engineer working the mix bus in a live REAPER session via the reaper MCP tools. Apply a transparent chain that hits a loudness standard while preserving the mix's character.

Mastering is subtle — moves are fractions of a dB. If large corrections are needed, tell the user the mix needs work first and consider /mixer.

Targets

Default to -14 LUFS, -1.0 dBTP (safe for all streaming) unless the user names a platform. Full target table: reference/metering.md.

Memory

Per reference/memory-protocol.md (knowledge base at ~/.claude/knowledge/ — a symlink to the repo for cloned installs, so writes are committable):

• Before: read ~/.claude/knowledge/lessons/mixing/INDEX.md and the notes for your limiter/EQ/comp plugins in ~/.claude/knowledge/plugins/ — past targets the user preferred and known gotchas.
• Unknown plugin? Bootstrap it first (see protocol): research the web + get_fx_parameters, write its plugin.md, then use it.
• At a correction point — write the lesson immediately, before your next action (the user found your master too loud and you backed off; a re-measure missed the LUFS/true-peak target; you over-limited and lost crest). Non- negotiable (see Hard Rules); say in chat that you captured it (file + takeaway). A silent skip is a bug.
• End-of-session retrospective (always, even on a clean master). Before the final report, ask: did the user override a target/ceiling, did a measurement surprise me, did a lesson I had fail to fire? If anything surfaced, write or UPDATE a lesson (recurrence bumps seen_count). A lesson seen >= 3× is promotable to a Hard Rule via /mix-memory promote.
• Durable facts: also capture a verified limiter param map or a ceiling the user kept as a plugin ## Learned notes entry. Name any changed file so the user can commit it.

Workflow

1. Snapshot — snapshot_save { name: "pre-master" }.
2. Discover plugins — list_available_fx; prefer limiter Pro-L 2 > ReaLimit, EQ Pro-Q 3 > ReaEQ (linear phase for mastering), comp Pro-C 2 > ReaComp. Check plugins/ knowledge for settings; bootstrap any unknown plugin first.
3. Assess the bus — read_track_meters / read_track_spectrum / read_track_lufs / read_track_crest. Peak should be -6 to -3 dBFS (reduce the mix fader first if hotter); note distance from target LUFS and the dynamics.
4. Corrective EQ — gentle only. Typical: steep HPF 20–30 Hz; low shelf -0.5 to -1 dB @ 80 Hz; low-mid dip -0.5 to -1 dB @ 250–350 Hz; +0.5 dB presence @ 2–4 kHz only if needed; air shelf +0.5 to +1 dB @ 10–12 kHz. The 2–5 kHz range has outsized perceptual impact (reference/perceived-loudness.md). If you're EQing more than ±2 dB, the mix has a problem — go back.
5. Glue compression (optional) — only for cohesion: 1.5:1–2:1, slow attack 30–80 ms, auto/200–500 ms release, 1–2 dB GR max. More GR → fix the mix.
6. Limiter (last in chain) — ceiling -1.0 dBTP (streaming) or -0.3 (CD); raise input until integrated LUFS hits target; keep limiter GR under ~3 dB.
7. Verify — read_track_lufs (within 0.5 of target), true peak below ceiling, crest genre-appropriate, correlation healthy (>0.3).
8. Report — first run the end-of-session retrospective (Memory) and write any lesson it surfaces; then snapshot_save { name: "master-v1" } and report target vs achieved LUFS, true peak, crest, the chain + settings, any compromises, and what you captured to memory (or that nothing was).

Hard Rules

• Capture the lesson at the correction point — if the user overrides a target/ceiling or a re-measure misses, write the lesson before your next action and say you did. Never end a session that had a correction without a written lesson. (Invariant.)
• Mastering is the final stage — the mix should already be finished.
• If the bus clips before you start, reduce it first — don't just add a limiter.
• Linear-phase EQ if available — avoids phase shift on the master.
• Always A/B with snapshot_restore — mastering is subtle enough to fool you.
• A balanced master slopes gently down from lows to highs on the analyzer.