The style of blues that developed out of the migration of workers from the south to the cities of the north, and was typified by small groups of musicians performing together, was called:

Spirituals or Work Songs

Explanation:

I'm guessing you mean songs like "Crossing Jordan" or "Wading trough the Water," which would both be considered spirituals. If it were a larger group (and sung in a call-and-response pattern) they would be work songs.

here's your

earliest

neumes above text

neumes

colored lines

neumes

4-line staff

f, c, or g clef

notes on 5-line staff with clef

mensuration (longas and breves)

time signature (perfect or half circle)

most recent

notes on 5-line staff

modern clefs

modern note values (whole, half, quarter, and so on)

modern time signature

italian words and abbreviations for dynamics and tempo

staccato, slurs, and so on