What is the song that plays second before they show Goku and Gohan Fishing together Dragon Ball Z Episode 154 No Worries Here That xylophone music I presume it instrument?

The song you're referring to is "Peaceful" from the Dragon Ball Z soundtrack. It's a very recognizable and calming melody that is indeed played on the xylophone.

It's often used in scenes of serenity and peace, like when Goku and Gohan are fishing, reflecting the peaceful moments within the story.

You can find the full song on various music platforms like YouTube and Spotify.