cornet - A wind instrument, like the French horn, is meant.
flute - a pipe or pipes, not blown transversely as our “flute,” but by mouthpieces at the end.
sackbut - a triangular stringed instrument, having short strings, the sound being on a high sharp key.
psaltery - a kind of harp.
dulcimer - a bagpipe consisting of two pipes, thrust through a leathern bag, emitting a sweet plaintive sound. Chaldee sumponya, the modern Italian zampogna, Asiatic zambonja.
fall down - that the recusants might be the more readily detected.