I want to work on vocal style but I mostly sing pop (or R&B, rock, country, alternative, folk, blues, or singer-songwriter.) How specific to jazz is the vocal style work?
All of the vocal style examples are with jazz songs, but the material is very relevant for other contemporary styles. R&B singers often improvise extended pentatonic runs. Country singers often add fills, or ornaments. Rock singers often add dives, vocal texture and substitution notes. Pop singers must stay aware of interpretation and dynamics. Folk singers often use subtle ornaments. Singer-songwriters often use all of these elements as well as phrasing. All of this and much more is covered in the vocal style section of Singing With Style.