Bass Guitar Tuner - E Standard Tuning (E A D G) 4 Strings - YouTube
Instrumentalist Royal Academy by Gideon keys - 5 - string bass guitar tuning 5 string basses are becoming more common. They can be tuned adding an extra low string B, E, A,
Bass guitar tuning - Wikipedia
Tuning your bass – Yousician Support
School of Rock | Beginner's Guide to Tuning a Bass Guitar