The longest single sample @ 44.1kHz/16-bit stereo is 64MB — That is precisely 6 minutes and 20 seconds.

From the article ... “Sampling in Sequencer Mode with the Motif ES“
With expansion capability of 512MB, you have more than 50 minutes of stereo record time at the highest resolution (44.1kHz), that’s over 100 minutes of mono recording. This means serious recording can be done. The Motif ES is a sampler, however, and a sampler is different from a hard disk recorder in many ways. They both are tools for music creation via recording audio. However, in a sampler in order to trigger playback you must use MIDI events. Any advantages that a sampler has over a HD recorder are not measured in record time (the HD recorder easily wins that contest every time), but in how you can manipulate and utilize the audio data that you record. It should be mentioned here there is a ‘limitation’ to the longest single sample that you can take – 6 minutes and 20 seconds. This is a 64MB stereo sample at 44.1kHz. This should not be a limitation really but recognize that you cannot open a mic and record for 50 minutes straight…if that is what you think you need, can we recommend a tape recorder or hard disk recorder like the AW16G!!! This is the reason we stress the point that this is still sampling and the art of sampling is quite a bit different from the art of Hard Disk recording

Extra Credit:
Sampling in Sequencer Mode Motif ES

I am so disappointed and discouraged now. I bought this keyboard years ago with the understanding that I would be able to record my own Piano music on one keyboard without purchasing recording equipment. It has taken me several years to get to this point to be able to figure it out...partly because of time schedules and also due to the fact that I am tecnically challenged. I need things simple. Today, for the first time I got my sound quality and settings exactly where I wanted them after many attempts, and finally got every step accurate to be able to get a recording that I was happy with, just to find out that what I purchased is'nt what I thought it was. All I used today was a piano pad setting....no microphones...only 1 track. I honestly have no idea what you are talking about in your paragrah, but I assume it requires purchasing more equipment and having to learn a bunch of new stuff that I will be challenged to have time for, let alone understand. You will have to explain things in simpler terms for me to be able to understand what it is that I have to do to get a recording that I can use, keeping it as simple as possible for this technically challenged person. I am wanting to make a recording each week..20 - 30 minutes in length. what do I need to do?

We can recommend (especially since most of what I wrote in the first answer is like *news* to you) — record yourself to the Motif ES using the MIDI sequencer. Then you can record your lengthy compositions. Once you have them recorded, you can mixdown to an audio format using any number of devices that can record linear audio.

I was just thinking about what’s happened in the 17 years since the Motif ES came out... if I told you, back in 2003 that you would be able to record a .wav of yourself playing your instrument to your Smart phone or tablet, you wouldn’t have believed me... you’d have asked, “What’s a Smart Phone?”

Using a sampler for what you want to do is like using a screwdriver when you need a hammer. A sampler is simply the wrong tool for your stated goal.

The “Full Grand“ acoustic piano sound is made with a sampler... As the name implies, it is to grab little bits of audio that are assembled into something. The total amount of record time (in minutes and seconds) to create the three velocity layers of that piano is less than the 6 minutes 20 seconds continuous record time. A sampler’s primary function is NOT linear record time, it’s maximized to recreate musical instrument sounds...a collection of little bits of audio assembled into a playable instrument, like “Full Grand”. Your Motif ES’s entire Wave ROM is a collection of 175MB of audio recording. Seventeen and a half minutes of stereo record time IF laid out linearly — but linearly is NOT how it is used.

For example, to sample a Brass Section, Yamaha called in Tower of Power to play each Note that you hit on one of the Brass section sounds... each half step is recorded, looped and set to play when you trigger the key. They did not come in and play “What is Hip?” they played whole notes, half step higher each sample.

The samples used to build instruments are different from linear audio recording because each sample is just one note (one pitch) mapped to one Key. Some times multiple samples are stacked to a note, each set to trigger at different velocities.

A sampler is maximized to playback audio immediately when you press a key. Samplers do not record musical rests (samples have no “dead air”. Silence occurs only when the sample is over. You perform the music, each sample plays one note, one pitch. A sampler is optimized to do this type of recording. A collection of Motif ES samples is called a Waveform. A piano might be 88 soft samples, layered with 88 medium strike samples, layered with a set of 88 hard strike samples.

You are not going to need to record your playing as a *sample*. You should record your data as MIDI Events to the Motif ES sequencer, then when you have completed it, played it back, made any corrections, then you can mix it down to a stereo audio .wav File.

If you thought you were going to “sample“ for 20 minutes continuously, that is not how it works. That is not how samplers work— not 17 years ago, not today. That’s like buying a car and thinking just because it’s a means of transportation, why doesn’t it allow you to fly or cross the ocean. ... because that is not what it was designed to do. Samplers have a different, quite focused use.

With the 64MB for single sample limit, You’ll find audio clips, drum loops, backing vocals, etc., are the kinds of things that lend themselves to this type of audio recording format. Certainly, it’s never been about doing 20-30 minutes of recording (Linear based recording). Ask around.

Anyone who recommended this to you probably based it on the fact that most popular tunes are 3-4 minutes in length, standard. They are thinking standard popular music.

If MIDI recording is not appealing to you — then simply connect the Motif ES to any number of devices that can record audio (as I mentioned your phone probably can do a very decent job). In the 17 years since the ES came out a lot has changed!

Ask for help locally:
Your local music store likely has a bunch of qualified folks probably looking for extra work (in these strange times) call them, see if you can’t get one of their qualified staff to help you record your data. If you don’t have the inclination or the time to invest in all it takes to record yourself.... ask for help.

Not only do music stores have qualified staff, I’ll bet you’ll find no shortage of help right in your own neighborhood. This way, they can be ‘engineer’ and you get to concentrate on your music.

One of the suggestions which may have seemed buried in techno-speak was to use a "tape recorder". These vary in quality. Usually higher quality "tape recorders" (digital recorders these days) have a sea of buttons. If a digital recorder for taking dictation is good enough - then these would be dead simple. Press the red circle button to record. Press the white square button to stop. Press the white sideways equal sign to pause. Press the sideways equilateral triangle to play. The same general interface familiar from the cassette tape days (and before). As dead simple you will be relying on the built-in microphone to record what you hear in the room. Hopefully mostly your ES and not the AC or hitting the keys or other noise. Most of these digital recorders have a "line in" jack. You'd have to start getting more techie to use that. Getting the right cable, adjusting the keyboard levels, etc. So maybe just steer clear of that unless the quality is unbearable.

The local box stores where you can also get bananas sells these digital recorders.

Any of the higher end digital recorders with 1/4" jacks (the same as the outputs on your ES) are probably going to be intimidating with the buttons, screen, and options. They've got all of the same familiar "tape recorder" buttons - but usually lots more. And I've found others have had issues using these things. So I wouldn't necessarily recommend unless you really can't get something more basic working (quality-wise).

Just for reference, the "higher end" digital recorders (more buttons and such), at the affordable end of the spectrum, go as low as around $100.