At the school where I was last year we tried this and it seemed to work very well:
The 5th graders were divided into 3 even groups, and assigned to band/theater arts/computer. Every 6 weeks they rotated and at the end of the semester they had "sampled" each elective. After Christmas they were allowed to choose the one they liked best and were assigned to that class for the remainder of the year. During their 6 week trial with me they learned some vocabulary, basic notation and how to count & clap rhythms. The ones that chose band second semester spent 3 weeks on recorders, and the rest of the year we tried out instruments/mouthpieces and took the Band Blastoff test. By the end of the semester they were placed on instruments, had a basic knowledge of reading music and were ready to start 6th grade (actual) beginner band this year.