video is part of visual album 'Straight Outta Oz'
Adam Lambert, Britney Spears and more lend vocals
all proceeds from track will be donated to charity
the pair were joined by singer Andra Day
pop star remembered tragedy with song "Purpose"
Olly Alexander says video has 'magical queer creative energy'
Marathon three-hour set packs hits, deep cuts
Wolf Trap concert planned for July 7
Out artist continues AMP residency
singer writes heartfelt message