Right component supplies the sound qí — exact phonetic match, no tone shift.
奇 itself stacks
大 over
可, originally a one-legged stance; that asymmetric-posture nuance is sometimes read into
骑 as sitting astride (one leg each side), though most analyses treat it as purely phonetic. Same phonetic in
椅 (chair),
寄 (send),
倚 (lean on).