How many {instrumentation} are to/by {harpsichord} ?
What is the number of harpsichord players in the instrumental?
How many instrumentation are by harpsichord?
SELECT ( COUNT ( ?m ) AS ?h ) { ?m property:instrumentation resource:harpsichord }
SELECT (COUNT(?sub) AS ?subs ) {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> ?sub .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P870> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q81982 .
} 

SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P870 wd:Q81982 }
74