IMSLP:API

You can access a list of composers and works present on IMSLP using the following two URLs:

List of people (composers, performers, editors, etc.): http://imslp.org/imslpscripts/API.ISCR.php?account=worklist/disclaimer=accepted/sort=id/type=1/start=0/retformat=<pretty|json|php|wddx>
List of works: http://imslp.org/imslpscripts/API.ISCR.php?account=worklist/disclaimer=accepted/sort=id/type=2/start=0/retformat=<pretty|json|php|wddx>

You can page through the list by changing the start value (this is the entry # that the results start from).
https://imslp.org/wiki/IMSLP:API
imslp.org
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2019-10-15T03:30:20Z
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https://imslp.org/wiki/IMSLP:API
response
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isPartOf: CC-MAIN-2019-43
publisher: Common Crawl
description: Wide crawl of the web for October 2019
operator: Common Crawl Admin (info@commoncrawl.org)
hostname: ip-10-67-67-33.ec2.internal
software: Apache Nutch 1.16 (modified, https://github.com/commoncrawl/nutch/)
robots: checked via crawler-commons 1.1-SNAPSHOT (https://github.com/crawler-commons/crawler-commons)
format: WARC File Format 1.1
conformsTo: http://iipc.github.io/warc-specifications/specifications/warc-format/warc-1.1/