A harmonium is a keyboard instrument that makes its sound with small metal tongues called reeds. Air is pushed past the reeds and they buzz; the sound is thin and slightly nasal, softer and less grand than a church organ. On the European kind you pump air with your feet on two pedals while your hands play, which means you must keep working the whole time or the sound dies away. It was very popular in the 1800s and early 1900s because it was far cheaper and smaller than a pipe organ, so small churches, chapels, schools and ordinary homes bought them. Then the piano and later the electric organ pushed it aside, and in the West it now feels like an old-fashioned instrument you meet in a village hall or a museum. In India it took a completely different road: there the harmonium sits on the floor, you pump the bellows with one hand and play with the other, and it is a living, everyday instrument in devotional singing and classical music. So if a student hears 'harmonium', which picture is right depends on where the speaker is. Note the pipes: it does not really have organ pipes at all — it only looks and sounds a little like a small organ.

簧風琴、腳踏風琴（腳踩踏板打氣的那種舊式小風琴）；印度音樂裡的那種手拉式的，一般就直接說「印度手風琴」或 harmonium。台灣老一輩學校用的「風琴」多半指的就是這個。