A musician can increase his credibility by producing quality music, building relationships with other professionals in the music industry, engaging with fans on social media, and performing live shows
regularly. 
these are some steps which can help a musician increase their credibility:

1. Create a professional website. Having an online presence is essential for any musician. Having a website is a great way to showcase your work, increase visibility and provide information about upcoming shows and releases.

2. Showcase your work. Find ways to showcase your work, such as performing at open-mic nights, uploading videos to YouTube, and playing gigs at local venues.

3. Connect with other musicians. Reach out to other musicians and build relationships. Collaboration is a great way to learn from and support each other, and it can open up new opportunities for both of you.

4. Build a fan base. Interact with your fans, respond to their feedback and make sure to stay in touch with them. This will help you build loyalty and trust.

5. Seek out press coverage. Connect with press and bloggers and offer them exclusive content and interviews. You can also research publications that cover independent music and submit your work to them.

6. Network with industry professionals. Attend industry events and get to know the people in the music industry. This will help you build relationships and increase your credibility.

7. Create a Wikipedia page for a musician. Make sure your profile is accurate and up-to-date. It’s a great way to showcase your accomplishments and build your credibility as a musician.