Thomas tank?

[boatgirl10]

This is a little weird and has had me flummoxed for years, anyone got a simple explanation? When my children were very young, they are all young adults now, we were looking at a Thomas Tank Engine book, the sort with buttons to press for different sounds. I pressed the theme tune button and instead of the Da da da da dada daaaaa we heard the tune of an old childrens hymn Tell Me The Stories Of Jesus. It happened just once and only my daughter was old enough to recognize what was going on. she still remembers it, though more my reaction than anything I guess. we both talk about it with a little trepidation but would love to know the logical explanation.