Good frequency. Posting multiple times per day at the moment. Most guitar posts feature a guitar hanging on the wall. Using multiple hashtags which is great.
Keep up the frequency and consistency! Posting multiple times per day is great.
Consider using a similar background for guitar photos by taking the guitar off the wall and putting it on a stand. This will help to create more of a common theme. Hashtags are great but could be using more. Use as many ‘guitar’ hashtags as you can eg #guitar #guitarist #guitaristsofinstagram etc
Consider asking a question with your posts to encourage engagement. For example “what do you think?” “what song would you play on this guitar?” etc etc
Always add in a “call to action” by asking followers to do something next such as “Click the link in our bio for more” or “Send us a message for pricing”