I want to set up a pi as a piano module to maybe put inside an old MIDI keyboard. Unfortunately, I can not yet afford the Pianoteq one, so I’m looking for an alternative. There seem to be some great sample sets out there but I’m wondering if anyone has set up a Pi piano and which one sounded best for them.
cheers,
rod.
Maybe there’s some good quality piano sound pack available for Fluidsynth, try searching around for it. 
Thanks, I’ll do that and report back when I find something.
You may have to trade off the smart modeling of PianoTeq for brute force multiple samples to get the feel of a piano. A Pi 4 with extra RAM may expand your options. The smallest samples you find are pitch shifting a single sample, giving sad results. (I am assuming there are suitable SF2 players for MOD)
Some free SF2, SFZ (Ogg compressed) samples are pretty good. (I tested a few of these on my desktop computer with Sforzando SFZ)
http://freepats.zenvoid.org/Piano/acoustic-grand-piano.html
(You might have to settle for the one .sf2 offering of the SalamanderGrandPiano, to play on a Pi “not included, and in particular: amplifier velocity tracking (amp_veltrack), noises of pedal, hammer and string resonance on key release.” the 310Mb .tar.xz archive extracts to a single 1.27 gig SF2)
Looking a little deeper.
I examined the external files of an equivalent SFZ version to the all in one SF2 package’s hidden content.
There are a total of 641 samples, including 16 separate velocity samples of each note (giving the nice dynamics) , there are also some mechanical sounds like a .455 sec. key release sample for each of 88 keys, a couple of pedal down and up sounds, there are also 3 sets of 23 fast release samples, that appear to devide the 69 active notes into 1/3 ranges. “HarmL,…” “HarmS…”, “HarmV…” "hammer and string resonance?)
All 41.5K, 16 bit samples. (the files could by perhaps 1/2 the size if they pared down all the zero volume decay periods)
A backup source.
http://download.linuxaudio.org/lau/SalamanderGrandPianoV2/
The smallest sfz, (84Mb unzipped file) option for: SalamanderGrandPianoV2_OggVorbis compressed.
Has good velocity dynamics (missing the bottom 19 near sub audible notes of the scale, no aftertouch or mod wheel.)
This guide will take you to the links in the above post
Perhaps the most practical source of SF2 pianos is the Soundfonts 4U page has a variety of pianos and qualities, some recently updated.
(The 47Mb Chateau Grand-SF-Lite-v1.0 is sufficient for my tin ear and lousy speakers, it may be a good first test)