The phrase "all by one lonesome" can be replaced with several synonyms. Some of the alternatives include "solo," "solitary," "alone," "lonely," "isolated," "single-handed," and "unaccompanied." The word "solo" is often used in the context of music or performance, while "solitary" describes someone who prefers to be alone. "Alone" and "lonely" both suggest a lack of companionship and social interaction. "Isolated" implies a separation from others, while "single-handed" indicates that someone is doing something without any assistance. Lastly, "unaccompanied" refers to being without a companion, escort, or chaperone. All of these synonyms provide different shades of meaning that can be used to convey the feeling of being all by oneself.