Another source of notes in Jazz songs is the arpeggios of the chords used by the accompaniment. Learning to sing arpeggios of all the various types of 7th chords is essential if you are serious about singing Jazz.
However, this is a long term project and is best tackled in short bursts along with your regular practice. Concentrated work on arpeggios for ten minutes per day will bring great results after a few months.
This kind of study is best done with a teacher who knows Jazz theory, but here’s something to get you started. Shown next is the same Blues in Bb but this time the arpeggios of all the chords have been added under the chord symbols. Learn each arpeggio individually and then try moving from one to another. Remember this is just an ear training exercise, not a melody you would sing when performing live.