TL;DR - If your main aim is to play something and have it play in a loop immediately after, the simplest option is to get a looper unit. If your main aim is to assemble a collection of loops during a performance that can subsequently be triggered at various points, it's probably best to have one person handling the recording while the other one plays and to give some post-recording space where the performer continues to play, before triggering the loop
I'll start by saying that this answer won't address your specific equipment, in order to avoid being "too localized" (as in: applicable only to folks who have this specific setup). Instead, I will outline the general method of achieving the desired result and leave it to you to figure out a workable solution in your specific case.
What you are trying to achieve can best be described as a "punch-and-loop" technique. Here's what it consists in:
A section of audio is designated for loop playback,
A punch record is performed over the loop. By "punch record" I mean a situation where recording is enabled and disabled during the course of playback, so that audio plays until the punch-in point (either designated beforehand on the timeline, or activated manually), past which new audio is recorded over the track until the punch-out point (again, preset or manual) after which the previous audio resumes playback.
The combination of the two techniques results in the newly recorded audio continuing to play in a loop after punch-out.
There is a number of hardware units available on the market - typically known as "loopers" - that perform exactly this function. In a typical looper, the operator manually activates a punch-in, which automatically sets loop start to the punch-in point. The input to the unit is subsequently recorded to internal storage until the operator activates a punch-out. The punch-out point is automatically set as loop end and looping playback begins immediately.
Notice that in order to duplicate the operation of a looper unit, your setup needs to do the following things:
- Allow you to manually punch in and out of recording (this is usually possible in a Digital Audio Workstation),
- Allow you to designate loop limits with the same action as punching (the same keypress, say). This doesn't appear impossible in most scenarios - for example, you may be able to designate MIDI controls to both actions - but would require a familiarity with the particular equipment/software being used,
- Allow you to trigger loop playback with the same action as your punch out. This is subject to the same considerations as point 2.
One thing to bear in mind when using loops in live performance is timing issues. Because a loop repeats constantly, any errors in timing quickly become apparent to the listener. This applies not only to the performance being recorded, but to the accuracy of punching in and out (for example, a slightly delayed punch out will ruin the flow between loop end and loop start). For this reason, it is advisable to have an external timing source - such as a sequenced beat or click track - as a guide for both the performer and the person performing the punch (in fact, the punch may be automated on the timeline).
I mention the foregoing in order to point out a possible way towards achieving the second use case put forward, namely: collecting several loops that may subsequently be triggered.
Many of the problems involved with trying to duplicate the operation of a looper unit can be avoided by simply choosing not to.
Let's look at a somewhat broader picture of how loop recording and playback during live performance may be executed:
- Begin playing your part,
- At an appropriate moment, punch in and begin recording the performance to be looped, punching out at the appropriate moment,
- Designate loop start and end,
- At the appropriate moment, begin loop playback.
What does this mean in practice? You don't need to record your loop and begin playback straight away. You can equally well record a portion of your live playing and activate looping playback when you're ready to stop playing, which may be some time after the loop was recorded. If you are using additional sequenced audio as part of your performance (a "backing track", as it were), both as an artistic element and a timing source for your loop recording, this can provide you with a bit of pause to set up and trigger looping after you've finished playing the "live" portion of your performance.
You don't make it clear whether you and your friend would be doing this together or separately, but if it's together then possibly you could handle the fiddly bits of the punches and loop setup (including assignment of individual loops to triggering controls) while he plays the drums and he, in turn, could handle things for you when your hands are busy on the keyboard.
Here's one way I can think of doing it, if your DAW allows you to change the "arm for recording" state of your tracks during recording/playback:
- Set up however many tracks you want to record loops on with the appropriate inputs and outputs,
- Set up a loop extent for whatever time you want,
- Arm whichever tracks you want to record and loop for recording,
- Begin a loop record and disarm your tracks at the end of the loop; this should leave you with looping playback of whatever you just recorded,
- Whenever you want to record a loop in another track, simply arm it for recording at the beginning of the loop.
This allows you to layer the various loops on top of one another and control what is heard by use of Mute/Solo controls as well as balance their levels with the volume faders etc. Do be aware, however, that such an approach forces you to have all loops be the same length.