| Document and Entity Information | Sep. 23, 2021 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0000066496 |
| Document Type | 8-K |
| Document Period End Date | Sep. 23, 2021 |
| Entity Registrant Name | MILLS MUSIC TRUST |
| Entity Incorporation State Country Code | NY |
| Entity File Number | 000-02123 |
| Entity Tax Identification Number | 13-6183792 |
| Entity Address, Address Line One | C/O HSBC Bank USA, N/A Corporate Trust Issuer Services |
| Entity Address, Address Line Two | 452 Fifth Avenue |
| Entity Address, Address Line Three | 452 Fifth Avenue |
| Entity Address, City or Town | New York |
| Entity Address, State or Province | NY |
| Entity Address, Postal Zip Code | 10018-2076 |
| City Area Code | (212) |
| Local Phone Number | 525-1349 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
