Simplify the following text for a Grade 7 native English-speaking person.
Original: Street barrel organs usually play 7 to 9 tunes , although small organs ( usually the older ones ) can play up to 15 tunes .
Simplified: Even a small hand carried organ could play six or eight tunes . Stationary barrel organs , built into large houses or churches , were larger pipe organs , and could play longer , and more serious music .