PMApub / Academy lessons / Module 3

Historical Accrued Mechanicals & Black Box

By PMApub Academy · Last reviewed 2026-10-13 · About 7 min read

Why Unmatched Royalties Exist

A streaming service knows which recording a listener played. What it often does not know is who wrote the song inside that recording, who owns each share, and which publisher represents it. That information lives in a different set of databases than the recording data.

When the connection between a recording and its composition owners is missing, wrong, or incomplete, the service cannot identify who to pay. Common causes include missing writer names, inconsistent song titles, absent identifiers, disputed ownership, and songs that were never registered anywhere.

What Historical Accrued Mechanicals Are

Before the Music Modernization Act reshaped streaming licensing, services were already accruing mechanical royalties for songs they had not been able to match. The money was held rather than paid. The portion that built up before The MLC began operating is commonly referred to as historical unmatched royalties or historical accrued mechanicals. Many people also call it the black box.

When the blanket license became available in 2021, services transferred their accrued unmatched amounts to The MLC; industry press reported the initial transfer at roughly $424 million. The MLC then took on the job of matching works and paying the people entitled to them. Unmatched royalties for usage on or after 2021 are also held by The MLC while it tries to match them. Exact totals and payout details are published by the organization, so check its latest reports instead of relying on a figure repeated from an old article.

What Happens to Money That Is Never Claimed

The law requires The MLC to keep trying to match works and locate owners. The MLC states that unmatched or unclaimed royalties from usage on or after January 1, 2021 are held for a minimum of three years while it searches, and that interest earned during that time goes to rightsholders.

After that holding period and continued search efforts, remaining unclaimed money may be distributed to publishers and self-administered songwriters using a market-share formula based on usage reporting. A publisher or administrator that receives such a distribution must pay or credit songwriters, and the MLC states the writer's share cannot be less than 50 percent of the payment attributable to that writer's works.

The MLC has said it plans to distribute in stages, starting with the post-2020 usage and addressing the older historical pool afterward. It publishes its schedule, so read the current timeline on its website rather than relying on a date from an article.

The practical point is that claiming early matters. If you claim a share before it is distributed, the MLC states you receive the royalties held for earlier periods plus interest, except for periods already distributed on a market-share basis. Once money has been distributed that way, it is not available to you.

How to Check Whether You Are Owed Money

1. List your songs. Include every composition you wrote or co-wrote, with alternate titles and the names you have used as a writer.
2. Join The MLC. You need a member account to claim works as a songwriter or publisher.
3. Search the public database. The MLC offers a public search that lets you look up works and see whether they are matched.
4. Look for gaps. A work may be listed with no matched writer, with a partial share, or not found at all.
5. Register or claim. Register works that are missing and submit claims for shares you own, with the correct splits.
6. Follow up. Respond to any questions from the organization and revisit after a few months to see changes.

An Example: Maya and the Old Releases

Years ago, Maya released an EP under a different spelling of her name and with a co-writer named Alex. She has since joined a PRO and a distributor, but she never registered those older songs for streaming mechanicals.

When she searches, she finds two of the five songs listed with no matched writers. She registers both with the correct titles and a 50-50 split with Alex, after asking him to confirm. She also finds that the other three are matched but list a misspelled title. She submits corrections. She has no promise that any money is waiting, because each case is different. But she has made sure her songs can be matched going forward, which is the real benefit.

Tips and Cautions

• Be skeptical of anyone who offers to find your black box money for an upfront fee. The official tools are available for you to use directly, and you can review any service agreement with an attorney.
• Agree on splits with co-writers in writing before registering. Disagreements slow payment.
• Keep records of when each song was written, released, and registered.
• Use consistent names, titles, and identifiers everywhere.
• Do not assume past money exists. Treat the search as housekeeping, not a windfall.

A tracking template, such as the implementation plan available through PMApub Academy, can help you turn this into a small project with deadlines and owners. This article is general education, not legal or financial advice, so talk with a qualified music attorney or accountant about your own situation.

For labels, managers, and teams

For a label, management company, or publisher, the black box question is really a catalog audit. The goal is to know, song by song, whether each composition you control is registered, matched, and fully claimed.

Run the audit in batches. Export your catalog register, then search the MLC public database for each title using alternate titles, former artist names, and writer names. Flag three categories: not found, found but no matched shares, and found with partial or incorrect shares. Assign each flagged song an owner on your team and a due date.

Paperwork is the usual blocker. Before registering older songs, locate the signed split sheets, publishing agreements, and any termination or reversion documents. If a former employee, ex-partner, or deceased writer is involved, ownership may need legal sign-off before you claim. Do not claim shares you cannot document.

Disputes are common on older catalog. If another party claims a share you believe is yours, resolve it with them directly and keep written records. Disputed works are typically held rather than paid, so do not wait.

If you work with writers who are not on your roster, tell them what you found. If you are a publisher or administrator that receives distributions, check your agreements for what the writer is owed and have an attorney confirm the accounting. Retain evidence of what you searched and when, in case a writer or auditor asks.

Treat the audit as recurring housekeeping. Re-run it after each new release batch and after any change of distributor or administrator.

Common mistakes to avoid

• Assuming there is guaranteed money waiting. Many songs have nothing unmatched, and some have only partial matches.
• Paying an upfront fee to a third party to find money you could search for yourself, without reading the contract or having an attorney review it.
• Claiming a share without written agreement from co-writers, which can create a dispute.
• Searching only by the current title or name and missing alternate titles and old artist names.
• Waiting, on the theory that unclaimed money sits forever. It can eventually be distributed to others on a market-share basis.
• Registering a song with a different title or spelling than your other registrations.
• Treating black box money and neighboring rights money as the same thing. They are different categories.
• Not keeping records of what you searched, claimed, and corrected.

Action checklist

1. Make a list of every song you wrote or co-wrote, with alternate titles and former names.
2. Locate split sheets and agreements for each song.
3. Create your MLC account and verify it.
4. Search the public database for each song.
5. Mark each as not found, found but unmatched, or partially claimed.
6. Confirm splits with co-writers in writing before you claim anything.
7. Register missing works and claim shares you can document.
8. Submit corrections for misspelled titles or wrong writer data.
9. Log every action with a date in your catalog register.
10. Return in a few months and repeat the search for new changes.

Key terms

• Black box: informal name for royalties that could not be matched to an owner and are held.
• Historical accrued mechanicals: unmatched mechanical royalties that built up before the blanket license took effect and were transferred to The MLC.
• Unmatched royalties: royalties for usage that could not be tied to a specific musical work or its owners.
• Unclaimed royalties: royalties for a matched work where some ownership shares have not been claimed.
• Disputed royalties: royalties on works where claims conflict, usually held until the owners resolve it.
• Market-share distribution: allocation of remaining unclaimed money to known owners in proportion to their share of usage.
• Holding period: the minimum time unclaimed royalties are held while efforts continue to find owners.
• Public search: the MLC's free tool for looking up works, shares, and match status.
• Self-administered songwriter: a writer who collects their own mechanical royalties without a publisher or administrator.
• Administrator: a company that registers and collects royalties on behalf of publishers or writers, for a fee.
• Split sheet: a signed record of each writer's percentage in a song.