Change text in a text layer with markers, possible?

If you have 20 songs in a video, you don't want to edit them in After Effects. AE is an animation, visual effects, and compositing application destined to create shots, not edit videos. The average comp a pro makes is one shot and short. Mine are almost always less than 5 seconds. I made one the other day that was only 40 frames. 

Do your effects on a shot in AE, Render the Comp, and Edit in Premiere Pro.

If you want a custom title to display the band name, open the Essential Graphics Panel, spend some time studying the Adobe tutorials and workflows for creating a MOGRT, and create one that you can use in Premiere Pro to add the names of the band. 

Creating a movie with 20 songs longer than a couple of seconds each in a single AE comp will be a workflow and rendering nightmare. It's the wrong tool for what you are describing. 

Source text can be keyframed like any other property, so I'm not sure what you are asking. And yes, if you wanted to go fancy it could be triggered with markers and expressions as well, but you'd still have to input your text somewhere. And for a measly 20 entries on a basic video the effort to create and apply the expression would have zero benefits over animating it directly or indeed having a few more layers. Anyway, you may want to read the online help on some basics.

Mylenium