I'm steadily learning the notation for keys in sheet music, the series of flats and sharps that show what key the song is in. Is there a shortcut to determine that a song will be using pentatonic scales (or some other non major or minor scale) based upon the key? As there is no such thing as a 'Dmaj pentatonic key', right?

So if I am playing a song in the key of Dmaj, is there a way to know if it would be using primarily notes from the Dmaj pentatonic. Or would I just work it out by reading the individual notes since the Dmaj pentatonic is a subset of Dmaj?

I know a good amount of rock music is based on the pentatonic scale, and that the pentatonic is made up of 5 notes from its related major or minor scale.

I stick mostly to classic and alternative rock and I don't remember seeing any songs using minor keys? Perhaps other genres of music they are more common. Could you give me an example or two of a song written in a minor key so I can train my 'slow learning' ears? I'm sure it's covered in Guitar Fundamentals but I guess I haven't made it that far yet.

The only thing I know about minor keys is that they are sad - thank you Spinal Tap!