tutorial typos

Author: jweather

etc/doc/tutorial/01-Welcome-to-Sonic-Pi.md

@@ -14,7 +14,7 @@ I perform with code in front of audiences. You can find one of my
 [Meta-eX](http://meta-ex.com) tracks in the examples.
 
 If you have any thoughts, or ideas for improving Sonic Pi- please pass
-them on - feedback is so helpful.. You never know, your idea might be
+them on - feedback is so helpful. You never know, your idea might be
 the next big feature!
 
 Finally, this tutorial is divided up into sections grouped by

etc/doc/tutorial/01.3-Learning-through-Play.md

@@ -2,7 +2,7 @@
 
 Sonic Pi encourages you to learn about both computing and music through
 play and experimentation. The most important thing is that you're having
-fun and befor e you know it you'll have accidentally learned how to
+fun, and before you know it you'll have accidentally learned how to
 code, compose and perform.
 
 ## There are no mistakes

etc/doc/tutorial/02.3-Durations-with-Envelopes.md

@@ -16,7 +16,7 @@ section). An amplitude envelope offers two useful aspects of control:
 
 The duration is the length the sound lasts for. A longer duration means
 that you hear the sound for longer. Sonic Pi's sounds all have a
-controllable amplitude envelope and the total duration of that envelope
+controllable amplitude envelope, and the total duration of that envelope
 is the duration of the sound. Therefore, by controlling the envelope you
 control the duration.
 
@@ -125,7 +125,7 @@ play 60, attack: 0.3, sustain: 1, release: 1
 
 ![ASR envelope](:/images/tutorial/env-attack-sustain-release.png)
 
-The sustain time is useful for important sounds you which to hold full
+The sustain time is useful for important sounds you wish to hold full
 presence in the mix before entering an optional release phase. Of
 course, it's totally valid to set both the attack and release arguments
 to 0 and just use the sustain to have absolutely no fade in or fade out

etc/doc/tutorial/03.3-Stretching-Samples.md

@@ -1,6 +1,6 @@
 # Stretching Samples
 
-Now we can play a variety of synths and samples to create some music
+Now that we can play a variety of synths and samples to create some music
 it's time to learn how to modify both the synths and samples to make the
 music even more unique and interesting. First, let's explore the ability
 to *stretch* and *squash* samples.