I can do this reliably for songs I've listened to recently (within the last couple of days), but after that I somehow "forget" the pitch. If I played a C scale

I can do this reliably for songs I've listened to recently (within the last couple of days), but after that I somehow "forget" the pitch. If I played a C scale on my guitar a few times in the morning every day, I could probably identify pitches correctly based on that reference. But I'd still need the reference.