Get the music sheet out, and sing or hum the words of the song exactly how you would sing it in your normal singing voice.

As you sing through the whole song, When you get to the Root note on the music sheet where you sing ‘Doh’ or what ever singing word is on the music sheet, stop singing, get your sax out and play each sax key, until you find the sax key that sounds like your singing ‘Doh’.

Example if Your singing ‘Doh’ sounds like an “E” key in the sax, then opt for using E Major or E Minor as the scale to play the song in. The reason for using E Major or E Minor and not any other Major/Minor scale is because it comfortably fits the range of your singing voice.

Different people sing comfortably in various singing ranges, so they will pick a different major/minor scale.

Next problem is the mood you are in. If you are in high spirits, your singing ‘Doh’ will pick a different scale, likewise if you are sad you will pick a different scale, however the scale you pick will still gravitate to your singing range.