How to start a field at "1" and increment the value by one on the following records.

I am writing a database to track my player piano rolls.  My main form is frmTitles which on which the Piano Roll title information is entered and then the subform is frmSongs on which the song information is entered.  The fields on frmSongs are (in order) SongPosition, SongTitle, SongType and SongLength.  

When I first enter the subform I would like the default value for SongPosition to be 1.  Then for each song after that have the SongPosition increment by 1 so that after the initial 1 I would have 2,3,4,5,6,7 etc. until all of the songs for that title are entered.  It would help if there was a way to error check so that the numbers are all in sequential order.  I have access 2016.