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[KEYBANK LOGO]                                                 AMENDMENT TO NOTE

                                                                    EXHIBIT 4.2

     This is an Agreement amending a certain Business Loan Note (the "Note," a
copy of which is hereby attached and incorporated as Exhibit A), dated the 26th
day of April, 1996, originally issued in the principal sum of Two Million and
NO/100--Dollars ($2,000,000) with KeyBank, a National Association of 100 South
Main Street, Ann Arbor, Michigan 48104 (hereinafter referred to as the "Bank"),
as payee and holder of said Note, and Mechanical Dynamics, Inc. of 2301
Commonwealth Blvd, Ann Arbor, MI  48108 as Borrower (hereinafter referred to as
the "Borrower").

     Borrower hereby agrees with Bank that effective as of the date below, and
with the consent of the Guarantors of the Note (if any), said Note is hereby
amended in the following particulars:

1.   The principal balance outstanding under the Note as of the date of this
     Amendment is $______________, and accrued and unpaid interest under the
     Note as of the date of this Amendment is $_________________.

2.   The rate at which the principal outstanding under the Note is accruing
     interest (which may be defined as the "Note Rate" in the Note) is hereby
     amended so that interest shall now accrue upon the outstanding principal
     from the date of this Amendment:

     (check the applicable box)

     [ ] At the floating rate of the Bank's Prime Rate, when and as announced by
         the Bank, plus ___% per annum;

     [ ] At the fixed rate of ___% per annum.

     However, any rates of interest provided in the Note relating to the payment
     of interest upon or after a default under the Note shall remain in full
     force and effect.

3.   The terms for repayment of principal and interest under the Note are hereby
     amended in the following particulars:

     (complete if applicable)

     (a) Interest is now payable under the Note as follows:

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     (b) Principal is now payable under the Note as follows:

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4.   The Note is additionally amended in the following particulars:

     (complete if applicable)

     KeyBank releases its Security Interest in Accounts Receivable, specifically
     the Security Agreement dated April 30, 1996.

5.   Except as expressly amended herein, all of the terms of the Note are hereby
     confirmed and ratified, and continue in full force and effect. The terms of
     this Amendment shall be fully integrated and incorporated into the Note.

6.   The terms of all instruments evidencing the collateral securing the
     repayment of the Note, including all security agreements, assignments,
     guaranties, mortgages, assignments of rents and leases, and any and all
     other collateral securing the repayment of the Note, shall remain in full
     force and effect and shall continue to secure the repayment of the Note.
     Any other agreements executed in connection herewith, including without
     limitation any Loan Agreements, shall remain in full force and effect.
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7.   The terms of this Amendment shall bind the parties hereto, and their
     assigns, successors and transferees.

8.   This Amendment to Note shall not be considered a payment in full or
     novation of the Note, and the outstanding indebtedness under the Note
     remains unpaid and due and payable from the Borrower.


Mechanical Dynamics, Inc.                  KeyBank National Association ("Bank")

By  /s/ James E. Vincke                     By  /s/ John J. Donnelly
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Its James E. Vincke, Vice President and CFO Its John J. Donnelly, Vice President
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Dated   September 25, 1996                  Dated   September 25, 1996
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By
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Its
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Dated
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                  GUARANTOR'S ACKNOWLEDGMENT AND REAFFIRMATION

I/We, the Guarantor(s), have read and understand this Amendment to the Note and
hereby acknowledge and agree to the terms, convenants and conditions contained
within. I/We also reaffirm the validity and enforceability of the Guaranty of
the Note which I/we delivered to the Bank, and I/we hereby agree and
acknowledge that there has been no act or omission by the Bank that has in any
way modified, waived or discharged my/our liabilities and/or obligations under
the Guaranty on this ________ day of ______________________, 19___. I/We have
no claims, counterclaims, set offs or defenses, either legal or equitable, as
an individual or as surety and/or guarantor, against the Bank in connection
with this Amendment, the Note, or any other documents related to the Note or to
the indebtedness outstanding under the Note.

By                                      By
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