Every traders know MACD(12,26), but not every traders know the others two ( MACD(6,19) and MACD(19,39). Combining the 3 periods MACD in one chart, may look very interesting.
quote from Gerald Appel book ;
You should maintain at least two MACD combinations a faster one for buying
AND a slower one for selling.
When market trends are very positive, Buy very fast AND Sell very slow. You can
employ the 6–19 combination for buying, OR you can employ the somewhat more
reliable 12–26 combination. The 19- to 39-Day combination is used for selling.
When market trends are neutral to somewhat positive, Buy fast AND Sell slow.
Use the 12–26 combination for buying. Use the 19–39 combination for selling.
When market trends are clearly negative, Buy fast AND Sell fast. You can use the
12–26 MACD combination for both buying AND selling, in which case you will
sometimes be selling before the slower-moving 19- to 39-Day MACD has
crossed from below to above 0. However, unless a stop-out takes place, the
12–26 MACD lines should generally rise above 0 as a precondition for a Sell.