"Sing, sing a song. Make it simple, to last a whole life long." (song lyrics from Karen Carpenter)
Thanks to Pandora, my kids are exposed to a lot of great toddler tunes. Music for kids can be silly, calming, repetitive or tell stories. There is so much great stuff out there, but today I want to encourage you to go BACK TO THE BASICS.
One important consideration for developing voices is the quality of singing that they are exposed to. I LOVE to jam to my favorite bands while I'm driving or cleaning, but I don't want those voices to be the only ones my toddler hears. Toddlers MIMIC and so what they hear is so important. Those tiny voices shouldn't be straining to match a gravely, shouting, or emblishment crazed soprano voice. Look for artists who sing in the middle range, whose voice is pure w/o computer enhancements and whose words are clearly understood.
One great example of the type of singing to expose your child to is Jill Trinka. Hop on over to Amazon to hear clips of some of her recordings, or purchase through one of my affiliate links to the right (THANK YOU!).
One of my favorite songs to sing with kids is "Simple Gifts." A traditional Shaker dance song, this simple song is easy to sing and provides a great basis for later study of American folk culture. Though she hasn't memorized the words yet, my toddler LOVES to dance to this song. Similar to "Ring around the Rosy" (another historical dance song sung in a modest range), this song is great for twirling! Text:
'Tis the gift to be simple, 'tis the gift to be free 'Tis the gift to come down where we ought to be, And when we find ourselves in the place just right, 'Twill be in the valley of love and delight. When true simplicity is gain'd, To bow and to bend we shan't be asham'd, To turn, turn will be our delight, Till by turning, turning we come 'round right.
Here's a nice rendition by another favorite female vocalist of mine, Alison Krauss: