@prefix mo: <http://purl.org/ontology/mo/> .
@prefix math: <http://www.w3.org/2000/10/swap/math#>.
@prefix log: <http://www.w3.org/2000/10/swap/log#>.
@prefix af: <http://purl.org/ontology/af/>.
@prefix ctr: <http://purl.org/ontology/ctr/>.
@prefix qm-vamp: <http://vamp-plugins.org/rdf/plugins/qm-vamp-plugins#> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
@prefix tl: <http://purl.org/NET/c4dm/timeline.owl#> .
@prefix vamp: <http://purl.org/ontology/vamp/> .
@prefix sig: <http://purl.org/ontology/signal/> .
@prefix sim: <http://purl.org/ontology/similarity/>.
@prefix event: <http://purl.org/NET/c4dm/event.owl#> .
@prefix dcterms: <http://purl.org/dc/terms/> .

_:transform_keydetect a vamp:Transform ;
    vamp:plugin qm-vamp:qm-keydetector ;
    vamp:step_size "32768"^^xsd:int ; 
    vamp:block_size "32768"^^xsd:int ; 
    vamp:sample_rate "44100"^^xsd:float ; 
    vamp:parameter_binding [
        vamp:parameter [ vamp:identifier "length" ] ;
        vamp:value "100"^^xsd:float ;
    ] ;
    vamp:parameter_binding [
        vamp:parameter [ vamp:identifier "tuning" ] ;
        vamp:value "440"^^xsd:float ;
    ] ;
    vamp:output qm-vamp:qm-keydetector_output_key .

:pick_second_key dcterms:description "a simple algorithm that takes as input (subject) a list of keys and keychange times and returns as output (object) the key change occurring immediately after the first"@en .

    
{
	?track1 mo:available_as ?af1 .
	?af1 mo:encodes ?signal1 .
	?signal1 a mo:Signal ;
    	mo:time [
        	a tl:Interval ;
        	tl:onTimeLine :signal_timeline_1
    		] .
    _:keychange1 a af:KeyChange ;
		event:time [ 
		    a tl:Instant ;
		    tl:onTimeLine :signal_timeline_1 ;
		    tl:at ?key_change_time1 ;
		] ;
		vamp:computed_by _:transform_keydetect  ;
		af:feature ?key1 .		
}

	ctr:cc
	
{
	?track2 mo:available_as ?af2 .
	?af2 mo:encodes ?signal2 .
	?signal2 a mo:Signal ;
    	mo:time [
        	a tl:Interval ;
        	tl:onTimeLine :signal_timeline_2
    		] .
    _:keychange2 a af:KeyChange ;
		event:time [ 
		    a tl:Instant ;
		    tl:onTimeLine :signal_timeline_2 ;
		    tl:at ?key_change_time2 ;
		] ;
		vamp:computed_by _:transform_keydetect  ;
		af:feature ?key2 .
} .

(?key1 ?key_change_time1) :pick_second_key ?pkey1 .
(?key2 ?key_change_time2) :pick_second_key ?pkey2 . 
{?pkey1 math:equalTo ?pkey2 } log:implies 
{_:keysimilarity a sim:Similarity ;
      sim:element ?track1 ;
      sim:element ?track2 .
      } .