Interior Designer/Architect to create internal decoration design for Classical Music Practice Pod

I am a professional opera singer and I am having a soundproof booth built in my garage. All the spec is sorted. What's missing is how it will look on the inside. My builders whilst lovely are not interior designers. I need this very small space to feel spacious and light. Especially given that there is only one tiny window which will be 30cmx30cm. The dimensions of the booth itself are: 3.30x2.80x2.40m (h) - this is in meters and centimeters. Because I am a classical musician I need live sound not dead sound so having exposed soundproofing sponge needs to be kept to a minimum (my soubdproofing needs have been met already anyway). This practice pod is essentially a blank canvas (my builder says it should look like a normal room - very unassuming) and I need help creating a space which is warm, light, and inviting; and that I can work in for many hours at a time without feeling like I am trapped and the space is small and encroaching. I need space for my piano and would love ample storage for my books and maybe a small desk as well. I am obsessed with tiny house principals so if clever use of the space can be had without looking tacky, extra points! I leave it to you to make me a masterpiece!