I tested out two brands of ear plugs last night. Etymotic ER2o and Alpine Music Safe.
Both are affordable (under $20). Both are non-custom fit. Both cut highs despite what the manufacturers say. Both affect the way you will hear music. In practice – on stage – playing guitar – the ER20 was the clear winner. Overall, the sound was balanced in the low to high mids. It was an ok experience playing with these ear plugs. With the Alpine – dynamics seemed to be squashed and the roll off of highs was more apparent. What the Alpine has going for it was comfort and looks. The Alpine fits well and doesn’t stick out as much as the ER20. The ER20 was harder to fit and it sticks out a fair bit.
In the end result, the sound is what matters. The ER20 is my choice for live band use when needed.
Note: Since everyone hears differently, try both of them yourselves and see which one is better for you.