Why is it common to hammer-on a second note on the base string of a sweep-picking part, and is there a technique to playing it correctly?

Question

For example, an excerpt from Animals as Leaders' CAFO—

    Db|                13 12
    Ab|             13       13             13       12       13
    E |          14             14       14       14       14    14
    B |       14                      14       14       14          14
    Gb| 12h15                      12
    B |

^{Don't mind the tuning—it's just a drop D tuning, 1.5 steps down. And it's not what Tosin Abasi uses. Also, only the beginning is relevant, but I may have more questions about the rest of this part, so I figure it's better to familiarize readers with the complete part and repeat it over separate posts than show fragments in each question. If it matters, the above are all sixteenth-triplets, for 7 eighth notes in total.}

I'm new to sweeping and a bit confused by the presence of this hammer-on in many sweep-picking examples and exercises. I feel like instead of being able sweep across all the strings at a constant rate, you have to awkwardly spend double the time on the base string because of the hammer-on.

Is it purely to complete the arpeggio that it's common? (I suspect that's the case.) If so, are there any techniques to "suspending" your picking hand just after the base string, before continuing through the rest of the strings? Trying to do it consciously is maddening!

Answer 1

I think you're right. The reason you need a hammer-on here is to get the full arpeggio. One other way to get these notes is to start with finger 4 on fret 12 string 5 and play the second note with finger 2 on fret 10 string 4:

The timing of the hammer-on on the top string, at the end of the arpeggio, might be easier, but it is quite a stretch, and then you have to jump up to twelfth position.

In reply to your general point, about having to "consciously" think about waiting longer on a string with two notes during a sweep picked arpeggio, I think the only way around it is to gradually build the speed up from very slow with a metronome, taking great care always to keep the rhythm even. Doing this, you should eventually find that the timing becomes automatic (i.e. something you don't have to think about). Also, this will be of great value if you want to do sweep picked scales, where every string has a number of notes played with hammer-ons (although you can of course find patterns for these with the same number of notes on each string which makes the timing more "even").