Potential Improvements

Informs friendsA. Provide a direct link from the event's platform to create a Whatsapp (or other social media) group chat to start the planning
Learns about a concertA. Provide thorough details about the venue, including its sustainability and accessibility B. Provide special offers for group tickets C. Provide concert's ranking on safety, comfort, etc. D. Provide additional info for people with disabilities
Makes the trip to the eventA. Conduct research during the event about participant's satisfaction with the event and its organization B. Offer sustainable solutions, like reusable cups, etc.
Organizes the whole tripA. Provide travel and accommodation advice B. Offer group full packages - including accommodation and travel
Purchases the event ticketA. When buying a ticket, allow for a selection of physical disabilities and types of assistance required B. Clearly inform the customer of their options in case the concert gets cancelled C. Connect purchasing the ticket with a secure payment system like Paypal D. Mail a digital ticket together with a check-list of recommended things to do and info about additional services