<PAGE>   1
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM 10-Q

                  QUARTERLY REPORT UNDER SECTION 13 OR 15(d) OF
                       THE SECURITIES EXCHANGE ACT OF 1934


FOR THE QUARTER ENDED SEPTEMBER 30, 1999  COMMISSION FILE NUMBER 2-22997


                              MILLS MUSIC TRUST
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             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)


          NEW YORK                                               13-6183792
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(STATE OR OTHER JURISDICTION OF                               (I.R.S. EMPLOYER
INCORPORATION OR ORGANIZATION)                               IDENTIFICATION NO.)


C/O HSBC BANK USA,   140 BROADWAY,   NEW YORK, NY                  10015
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   (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)                      (ZIP CODE)


REGISTRANT'S TELEPHONE NUMBER, INCLUDING AREA CODE                (212) 658-6014
                                                                  --------------


     Indicate by check-mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange act of
1934 during the preceding 12 months (or for such shorter period that the
registrant was required to file such reports), and (2) has been subject to such
filing requirements for the past 90 days.

                               YES  X       NO
                                  -----       -----

NUMBER OF TRUST UNITS OUTSTANDING AS OF SEPTEMBER 17, 1999              277,712
                                                                       ---------
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                                                                          Page 2

                          PART I - FINANCIAL STATEMENTS

Item 1.  Financial Information

                                MILLS MUSIC TRUST
                  STATEMENTS OF CASH RECEIPTS AND DISBURSEMENTS
         THREE MONTHS AND NINE MONTHS ENDED SEPTEMBER 30, 1999 AND 1998

                                   (UNAUDITED)

<TABLE>
<CAPTION>
                           Three Months Ended        Nine Months Ended
                              September 30              September 30
                           ------------------        -----------------
                            1999      1998             1999      1998
                            ----      ----             ----      ----

<S>                       <C>       <C>               <C>       <C>
Receipts:
 Mills Music, Inc.        $225,547  $278,631          $759,444  $751,562

Undistributed cash
 at beginning of
 the period                     26        11                39         8

Disbursements -
administrative
expenses                  ( 11,609) (  3,433)         ( 35,640) ( 23,304)
                           --------  --------          --------  --------

Balance available
 for distribution          213,964   275,209           723,843   728,266

Cash distribution
 to unit holders           213,939   275,198           723,818   728,255
                           -------   -------           -------   -------

Undistributed cash at
  end of the period        $    25   $    11           $    25   $    11
                           =======   =======           =======   =======

Cash distribution per
 unit (based on 277,712
   units outstanding)      $   .77   $   .99           $  2.61   $  2.62
                           =======   =======           =======   =======
</TABLE>






    See accompanying Notes to Statements of Cash Receipts and Disbursements.
<PAGE>   3
                                                                          Page 3

                                MILLS MUSIC TRUST
             NOTES TO STATEMENTS OF CASH RECEIPTS AND DISBURSEMENTS
         THREE MONTHS AND NINE MONTHS ENDED SEPTEMBER 30, 1999 AND 1998

                                   (UNAUDITED)

NOTE 1.   ACCOUNTING POLICIES AND GENERAL INFORMATION

               Mills Music Trust ("the Trust") was created in 1964 for the
          purpose of acquiring the rights to receive payments of a deferred
          contingent purchase price contract obligation payable by Mills Music,
          Inc. ("Mills"). The contingent payments are determined quarterly, and
          are based on a formula which takes into account gross royalty income
          from certain music copyrights and licenses of Mills, less royalties
          paid and amounts deducted by Mills in accordance with contract terms.

               Payments from Mills to the Trust are made in March, June,
          September, and December, and include net royalty income of the
          preceding calendar quarter. The payments received are accounted for on
          a cash basis, as are expenses paid. The Declaration of Trust requires
          the distribution of all funds received by the Trust to the Unit
          holders after payment of expenses.

               The statements of cash receipts and disbursements reflect only
          cash transactions and do not present transactions that would be
          included in financial statements presented on the accrual basis of
          accounting, as contemplated by generally accepted accounting
          principles.

               There is no book value per unit because cumulative distributions
          are in excess of the initial investment in the Trust.

NOTE 2.   RELATED PARTY TRANSACTIONS

               The Declaration of Trust provides that each trustee shall receive
          reimbursement for expenses reasonably incurred in the performance of
          his duties and annual compensation of $2,500 per year for his services
          as trustee, provided that such aggregate compensation to the trustees
          as a group may not exceed 3% of the monies received by the Trust in
          any year. The Declaration of Trust further provides for reimbursement
          to the corporate trustee for its clerical and administrative services
          to the Trust. Accordingly, Marine Midland Bank receives reimbursement
          for such services and for services performed as Registrar and Transfer
          Agent. The Declaration of Trust further provides that if any trustee
          performs unusual or extraordinary services, reasonable compensation
          for such services shall be paid, subject to certain
<PAGE>   4
                                                                          Page 4

                                MILLS MUSIC TRUST
             NOTES TO STATEMENTS OF CASH RECEIPTS AND DISBURSEMENTS
         THREE MONTHS AND NINE MONTHS ENDED SEPTEMBER 30, 1999 AND 1998

                                   (CONTINUED)

                                   (UNAUDITED)

          limitations and to prior confirmation by a majority in interest of
          Trust Certificate holders. Pursuant to these provisions, disbursements
          to related parties were made as follows for the nine months ended
          September 30, 1999 and 1998.

<TABLE>
<CAPTION>
                                              1999        1998
                                             ------      ------
<S>                                         <C>          <C>
          Trustee Fees:
               Bernard D. Fischman           $1,875      $1,875
               HSBC Bank USA                  1,875       1,875


          HSBC Bank USA
               Transfer agent and registrar  $3,794           0
</TABLE>




NOTE 3.   FEDERAL INCOME TAXES

               No provision for income taxes has been made since the liability
          is that of the unit holders and not the Trust.
<PAGE>   5
                                                                          Page 5

                          PART I - FINANCIAL STATEMENTS

Item 2.  Management's Discussion and Analysis of Results of Operations

               The Trust's receipts from Mills Music, Inc. are derived from
          copyrights established prior to 1964 and such receipts fluctuate based
          upon public interest in the "nostalgia" appeal of older songs.

                           PART II - OTHER INFORMATION

               Items 1 through 6, inclusive, are not applicable.
<PAGE>   6
                                                                          Page 6

                                   SIGNATURES

     Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned, there unto duly authorized.

                                                        MILLS MUSIC TRUST
                                                  ------------------------------
                                                           (Registrant)



Date October 21, 1999                         By:      BERNARD D. FISCHMAN
     --------------------                         ------------------------------
                                                  Bernard D. Fischman, Trustee



Date October 21, 1999                         By:        MARCIA MARKOWSKI
     --------------------                         ------------------------------
                                                  HSBC Bank USA
                                                  Corporate Trustee