Oyster sauce salt, should be added to the sauce, since the oysters should provide all the savoury flavour. However, this method is prohibitively expensive. Many modern oyster sauces are thickened with cornstarch, flavoured with oyster essence or extract and darkened with caramel. Vegetarian oyster sauce prepared from mushrooms, often oyster mushrooms or shiitake mushrooms, is also popular and generally lower in price. It may contain more taste enhancers if less mushroom extract is used to reduce costs. Most of the oyster sauces available on the market contain added monosodium glutamate (MSG). In recent years MSG-free varieties can also be found. The taste
Diatonic button accordion like a harmonica. Other single-action or bisonoric members of the free-reed family include the German concertina, the Anglo-German (or "Anglo") concertina, the bandoneon, and the Chemnitzer concertina (see concertina). There are varieties of diatonic button accordion that are double-action, such as the garmon. Because each button produces two notes, the diatonic scale can be covered in four buttons on a melody row. For example, on a melody row pitched in C, the notes of the lower full octave of the instrument's range are assigned to four buttons as follows: "Note: the first button in the example above, numbered 1, is