That took me back to the days when our boys were young Cub Scouts and I was a den leader. Being a Cub Leader is strenuous, but a lot of fun. The BSA is so well organized and has great helps and instructions. All you really need do is follow the guidebook and monthly calendar and you too can be a success! My favorite meetings, though, were the ones in which I could help the boys explore their musical gifts. We sang silly songs. We created whacky musical instruments. We explored rhythm and notation. We even performed for Pack Meetings.
When looking for tunes, they should be short, catchy, and have a melody with very steady beats. Beethoven's famous "Ode to Joy" theme from his 9th Symphony is a favorite. It can be played with steady quarter note beats, but only has 5 pitches. Another favorite was "Joy to the World" - also played with simplified rhythms - but it has eight pitches. Other fun tunes are: "Good King Wenceslas," "Up On the Housetop," "Jingle Bells," "Lightly Row," "Are You Sleeping, Brother John," and "Bingo." A song like "On Top of Old Smokey" can also be use to explore harmony. We had half of the group or the audience sing the melody, while the boys played "omm pah pah" rhythms on the bottles. We had the first beat (oom) played low, usually F, G or C, with the upper notes of the triad played on beats 2 and 3 (pah pah). For inspiration, try looking in beginner piano or recorder instructional books for more songs.
I have used these methods for forming Pop Bottle Bands with other groups, too. The Young Women and their leaders at Girl's Camp were able to do more advanced songs because many of them already played wind instruments and had better skills than the little Cub Scouts. Youth Groups, School groups and Family groups can give amazingly polished performances with very little practice. It can be fun for everybody -- careful, though, for it can quickly become a free for all!
WARNING! Creating a Pop Bottle Band may become habit-forming and from then on you may always be on the look-out for deep-toned bottles!