What are these black keys doing in C major?

array(10) { [0]=> object(stdClass)#5370 (5) { ["video_id"]=> int(9999999) ["related_video_id"]=> string(11) "XnGruesONZo" ["related_video_title"]=> string(32) "Better tools for writing harmony" ["posted_time"]=> string(19) "1 год назад" ["channelName"]=> string(13) "Piano Fluency" } [1]=> object(stdClass)#5343 (5) { ["video_id"]=> int(9999999) ["related_video_id"]=> string(11) "d1Bt9rAgMZs" ["related_video_title"]=> string(33) "The fastest way to train your ear" ["posted_time"]=> string(19) "1 год назад" ["channelName"]=> string(13) "Piano Fluency" } [2]=> object(stdClass)#5368 (5) { ["video_id"]=> int(9999999) ["related_video_id"]=> string(11) "6OSDbarIiYs" ["related_video_title"]=> string(39) "6 Chord Progressions in the DORIAN Mode" ["posted_time"]=> string(21) "2 года назад" ["channelName"]=> string(11) "Mike George" } [3]=> object(stdClass)#5375 (5) { ["video_id"]=> int(9999999) ["related_video_id"]=> string(11) "GKOZhCbR4i8" ["related_video_title"]=> string(94) "Туториал по Аккомпанементу | От простого к сложному" ["posted_time"]=> string(19) "3 дня назад" ["channelName"]=> string(25) "TG PRODUCTION MUSIC WORLD" } [4]=> object(stdClass)#5354 (5) { ["video_id"]=> int(9999999) ["related_video_id"]=> string(11) "OlOipKxfF7o" ["related_video_title"]=> string(44) "This Chord is THE Sound of the Romantic Era!" ["posted_time"]=> string(27) "7 месяцев назад" ["channelName"]=> string(9) "Josh Cook" } [5]=> object(stdClass)#5372 (5) { ["video_id"]=> int(9999999) ["related_video_id"]=> string(11) "-7ynGnfs5Eg" ["related_video_title"]=> string(38) "Why this is my favorite piano exercise" ["posted_time"]=> string(19) "1 год назад" ["channelName"]=> string(13) "Piano Fluency" } [6]=> object(stdClass)#5367 (5) { ["video_id"]=> int(9999999) ["related_video_id"]=> string(11) "TOp-fsgnHIE" ["related_video_title"]=> string(32) "Learn any song by ear in 3 steps" ["posted_time"]=> string(19) "1 год назад" ["channelName"]=> string(13) "Piano Fluency" } [7]=> object(stdClass)#5377 (5) { ["video_id"]=> int(9999999) ["related_video_id"]=> string(11) "kqtOvCBEtSI" ["related_video_title"]=> string(173) "[ НОВЫЙ 2025 ] Уральские Пельмени -Смейтесь без остановки вместе с комедийной группой №1 в России!" ["posted_time"]=> string(21) "1 день назад" ["channelName"]=> string(16) "Hanif Islamic Tv" } [8]=> object(stdClass)#5353 (5) { ["video_id"]=> int(9999999) ["related_video_id"]=> string(11) "HOH09vjRuQ4" ["related_video_title"]=> string(65) "How To Use Secondary Dominants, Diminished 7ths and Cycle of 5ths" ["posted_time"]=> string(19) "8 лет назад" ["channelName"]=> string(10) "Rick Beato" } [9]=> object(stdClass)#5371 (5) { ["video_id"]=> int(9999999) ["related_video_id"]=> string(11) "ujB8QukPdV4" ["related_video_title"]=> string(27) "How to use numbers in music" ["posted_time"]=> string(19) "1 год назад" ["channelName"]=> string(13) "Piano Fluency" } }