Yup.
Its in your finger attack [and pick].
I use an American Standard P Bass with an Edan rig set flat., dead strings Bass players and soundman have asked be how do I get that tone ?
I have not changed my strings since I bought my new bass in 2000 and I gig approx. 6-7 times a month.It has a really nice warmth now.
James Jamerson NEVER changed his strings. [he used flat rounds]