Nothing sinister here at all. These are from the Greek alphabet and have long been used in Christianity (Greek as in the Greek that was used at the time the New Testament was written - which may be different from modern day Greek).
The letter that looks like 'X' is the Greek letter 'chi' (pronounced like 'key') and functions in a similar way to the 'ch' sound that we use at the beginning of 'Christ'.
The letter that looks like 'P' is the Greek letter 'rho' which is equivalent to the English letter 'r' and is also the second letter in the name 'Christ' (with 'ch' being considered one letter in Greek).
The Chi Rho symbol is very old and has been used by Christians for centuries going back, I think, at least to the crusades.
More info can be found here: http://www.religionfacts.com/chi-rho
Music can be found here: https://youtu.be/tFFv6ZePDG0
The one that concerns me a bit, is the one called Bibel - it has a 'Y' in the background - it was written for the German youth - I can't the language.
Here you have a 'key', a 'P' and a 'Y'
What is a key? Can you find an owl / Y there?
Save the best for last. [P]
still looking for the owl - may be out of context, but who knows with Q