EMusic said it developed its "acoustic fingerprinting" technology after the break down of discussions between the two companies on unauthorized distribution of songs licensed to EMusic. The fingerprinting software will be used to identify songs on the Napster service that EMusic says infringe copyright laws.
Cut off Gene Hoffman, president and chief executive officer of EMusic, said: "Napster's unfortunate and inflexible response has meant EMusic's only course of action is to request that offending users' accounts be cut off completely."
Napster officials could not be reached for comment.
Napster's client software allows users to trade music in a non-commercial format, which has proven controversial.
EMusic, meanwhile, charges users for licensed titles per-song, per-album, or by a subscription-based fee. Single songs on the site cost 99 cents, with albums costing $8.99.
EMusic also offers users a $9.99 subscription service, involving unlimited downloads of around 140,000 licensed titles.