- Bernstein - Maria: https://youtu.be/DyofWTw0bqY (incredible use of "augmented fourth" or tritone - "the devil in music")
- Beatles "Something" - https://youtu.be/X5IVp25InsA Some surprising "modulation"
- Rogers & Hammerstein "Do-re-mi" - that most diatonic of all tunes throws in a B Flat at the end if you play it in C major. https://youtu.be/drnBMAEA3AM
PS - an internationally respected and tenured musicologist friend of mine has pointed out there is more than just the B flat chromaticism in "Do-re-mi":