A hammer-on is a technique where the first note is picked but the second note sound is produced by "hammering" the left hand finger onto the fretboard. The hammer-on is indicated on the music staff by a curved line joining two different notes. In tab notation the hammer-on is indicated by a curved line and the letter H above it. A hammer-on is sometimes called an ascending slur.
The hammer-on is performed by playing the first note with the right hand (as in the next example - a G note on the fifth fret of the 4th string). While this note is still sounding, the third finger of the left hand hammers down onto the second note (an A note on the seventh fret of the 4th string). The second note is not picked; the sound is produced entirely by the left hand "hammering" onto the string as shown in the diagrams.
Remember that the second note is not played by the right hand, the sound is produced entirely by the third finger "hammering" onto the string. You will need to be careful with the timing of the hammer-on. Both the G and A notes are eighth notes and each should have an equal time value when played (regardless of the hammer-on technique).
The most famous of all combo amps is the Fender Twin Reverb. It produces a crisp clean tone, even at high volumes and is used by players of many different musical styles. Many players use a Fender Twin as their basic sound and combine it with pedals to achieve distortion and other effects.