The International Standard Music Number (ISMN) is a unique identifier for notated music (scores, parts, vocal scores, choral octavos, miniature scores, pop folios, etc.) whether published in print, online, or in other media. Each edition or version of a musical work is assigned a separate ISMN.  Each separately available constituent part of a publication is assigned its own ISMN. 

The ISMN is useful in music publishing, the music trade, and libraries. It is used for inventory, ordering, billing, rights assessment, information retrieval, library circulation, and inter-library loan. The ISMN serves as a unique identifier for a monographic publication, from manuscript stage through editorial and manufacturing processes until the work is finished.

The U.S. ISMN Agency at the Library of Congress assigns ISMN identifiers to publishers and individual ISMN to notated music items published in the United States.

The ISMN is provided free of charge to United States music publishers, in all states and territories.  All interactions for publisher registration and ISMN assignment take place via this website.

Advantages of the ISMN

• The ISMN is used world-wide, as a standard, unique identifier allowing precise communication across languages, scripts, cultures, borders.
• The ISMN is a very mature system, having been introduced as an international standard in 1993.  It is widely used across European and elsewhere in the music publishing world.
• The ISMN is administered in a straightforward, uniform way by the International ISMN Agency, in Berlin.  Thus it functions seamlessly and without confusion from one country to another.
• The ISMN is a requirement in some markets.  Its presence on U.S. imprints opens doors to international commerce.
• The ISMN Archive, maintained at the Library of Congress, ensures continuity of public access to information about U.S. music publications.
• ISMN Archive data, provided by publishers themselves, is structured such that it can be re-purposed efficiently.
• ISMN Archive data is re-purposed seamlessly into Library of Congress online catalog records.  Items with ISMN can be fast-tracked into the permanent collections of the Music Division of the Library of Congress.
• The ISMN is used as a first search parameter by Library of Congress staff and many others, worldwide.
• It's free. It's easy. It's good for business.

Numeric Structure

ISMN are comprised of 13 digits divided into four elements and are printed as in this example:

• Prefix element (always 979-0, denoting music)
• Publisher element (variable in length; 2600, in this example)
• Item element (variable in length; 0043, in this example)
• Check digit (validating the number; 8, in this example)

Like the ISBN (International Standard Book Number), the ISMN is a “smart” number, containing a publisher identifier.  Unlike the ISBN, the ISMN contains no area/language prefix, as music is intrinsically international, suggesting no geographic/linguistic boundaries.

Prolific publishers receive an identifier of three or four digits; smaller publishers receive identifiers of five, six, or seven digits.

Check digit calculation

The math for computing the check digit is based on a simple modulus 10, with alternating weights of 1 and 3 assigned from left to right.  Each of the first 12 digits (excluding the check digit itself) is multiplied by an alternating sequence of the numbers 1 and 3, from left to right.  The sum of the products thus obtained, plus the check digit, must be divisible, without remainder, by 10.   For example:

	prefix element	publisher element	item element	check digit
ISBN	9  7   9  0	2  6  0  0	0  0  4  3	8
Weight	1  3   1  3	1  3  1  3	1  3  1  3
Products	9+21+9+0	+2+18+0+0	+0+0+4+9	= 72

Total: 72 + 8 = 80 --> 8 = check digit

The U.S. ISMN Agency provides publishers with valid numbers, complete with appropriate check digits already calculated.

Prior to January 1, 2008, ISMN consisted of ten digits, divided into four elements, and printed as in this example (on the right). These older ISMN are often encountered on earlier music publications and function just as the currently used 13-digit numbers.