Put Our Märta First or As Luck Will Have It(1945)

Original title: Fram för lilla Märta eller På livets ödesvägar

An out-of-work musician is desperate for work and when his best friend sees an add requesting a cellist he signs him up. However, the work is for a female, so he creates the character Märta Letterström and joins the trio at a small-town hotel. But being a woman is not as easy as you think.