We prioritize reducing our impact before compensation. We choose trains over flights whenever possible. And of course we use a green rider. An example can be found here. To offset our carbon footprint, we rely on Julie's Bicycle's carbon footprint calculator, which accurately considers travel, accommodations and electricity usage during concerts.
For immediate CO2 emissions, we trust Atmosfair, an environmentally conscious organization that invests in renewable energies in underdeveloped countries rather than planting trees which need to grow first for decades to be able to absorb CO2 . By doing so, they reduce CO2 emissions caused by fossil fuel consumption and provide clean energy to local communities, fostering education and equal opportunities.
We also use Atmosfair to calculate and compensate for our flights.
Although we haven't accounted for the audience's travel impact, we're exploring ways to encourage carpooling and public transportation, as it can have a wider effect on travel behavior. Feel free to share your knowledge and ideas on this topic in the comments below.